diff --git a/lib/builtin.js b/lib/builtin.js
index 73bb61f..58e361e 100644
--- a/lib/builtin.js
+++ b/lib/builtin.js
@@ -19,6 +19,7 @@ import * as createGroups from '../plugins/createGroups.js';
 import * as inlineStyles from '../plugins/inlineStyles.js';
 import * as inlineUse from '../plugins/inlineUse.js';
 import * as mergePaths from '../plugins/mergePaths.js';
+import * as mergeGradients from '../plugins/mergeGradients.js';
 import * as minifyColors from '../plugins/minifyColors.js';
 import * as minifyGradients from '../plugins/minifyGradients.js';
 import * as minifyPathData from '../plugins/minifyPathData.js';
@@ -82,6 +83,7 @@ export const builtin = Object.freeze([
   createGroups,
   inlineStyles,
   inlineUse,
+  mergeGradients,
   mergePaths,
   minifyColors,
   minifyGradients,
diff --git a/lib/css.js b/lib/css.js
index 56be31c..c4d52f7 100644
--- a/lib/css.js
+++ b/lib/css.js
@@ -5,7 +5,6 @@ import {
 } from './svgo/tools.js';
 
 /**
- * @typedef {import('./types.js').XastElement} XastElement
  * @typedef {import('./types.js').CSSFeatures} CSSFeatures
  * @typedef{{type:'AttributeSelector',name:string,matcher:string|null,value:string|null,flags:string|null}} AttributeSelector
  * @typedef{{type:'ClassSelector',name:string}} ClassSelector
@@ -15,7 +14,6 @@ import {
  * @typedef{{type:'TypeSelector',name:string}} TypeSelector
  * @typedef{AttributeSelector|ClassSelector|IdSelector|PseudoClassSelector|PseudoElementSelector|TypeSelector} SimpleSelector
  * @typedef {import('./types.js').CSSDeclarationMap} CSSDeclarationMap
- * @typedef {XastElement&{style?:string,declarations?:CSSDeclarationMap}} XastElementExtended
  */
 
 export class CSSRuleSet {
@@ -78,6 +76,19 @@ export class CSSRuleSet {
     return false;
   }
 
+  /**
+   * @param {string} id
+   * @returns {boolean}
+   */
+  hasIdSelector(id) {
+    for (const rule of this.#rules) {
+      if (rule.hasIdSelector(id)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   #initFeatures() {
     const features = new Set();
     if (this.#atRule) {
@@ -108,7 +119,7 @@ export class CSSRule {
   #specificity;
   #declarations;
   #isInMediaQuery;
-  /** @type {(function(XastElement):boolean)|undefined} */
+  /** @type {(function(import('./types.js').XastElement):boolean)|undefined} */
   #matcher;
 
   /**
@@ -205,12 +216,19 @@ export class CSSRule {
     return this.#selector.hasAttributeSelector(attName);
   }
 
+  /**
+   * @param {string} id
+   */
+  hasIdSelector(id) {
+    return this.#selector.hasIdSelector(id);
+  }
+
   hasPseudos() {
     return this.#selector.hasPseudos();
   }
 
   /**
-   * @returns {(function(XastElement):boolean)|undefined}
+   * @returns {(function(import('./types.js').XastElement):boolean)|undefined}
    */
   #initMatcher() {
     const sequences = this.#selector.getSequences();
@@ -241,7 +259,7 @@ export class CSSRule {
   }
 
   /**
-   * @param {XastElement} element
+   * @param {import('./types.js').XastElement} element
    * @return {boolean|null}
    */
   _matches(element) {
@@ -252,7 +270,7 @@ export class CSSRule {
   }
 
   /**
-   * @param {XastElement} element
+   * @param {import('./types.js').XastElement} element
    * @return {boolean}
    */
   // eslint-disable-next-line no-unused-vars
@@ -352,6 +370,13 @@ export class CSSSelector {
     return this.#selectorSequences.some((s) => s.hasAttributeSelector(attName));
   }
 
+  /**
+   * @param {string} id
+   */
+  hasIdSelector(id) {
+    return this.#selectorSequences.some((s) => s.hasIdSelector(id));
+  }
+
   hasPseudos() {
     return this.#strWithoutPseudos !== undefined;
   }
@@ -485,6 +510,18 @@ export class CSSSelectorSequence {
     return false;
   }
 
+  /**
+   * @param {string} id
+   */
+  hasIdSelector(id) {
+    for (const selector of this.#simpleSelectors) {
+      if (selector.type === 'IdSelector') {
+        return selector.name === id;
+      }
+    }
+    return false;
+  }
+
   /**
    * @param {Map<string,string>} idMap
    */
@@ -512,29 +549,3 @@ export class CSSParseError extends Error {
     super(message);
   }
 }
-
-/**
- * @param {XastElementExtended} element
- * @param {CSSDeclarationMap} properties
- */
-export function writeStyleAttribute(element, properties) {
-  let style = '';
-  for (const [p, decValue] of properties.entries()) {
-    if (style !== '') {
-      style += ';';
-    }
-    style += `${p}:${decValue.value}`;
-    if (decValue.important) {
-      style += '!important';
-    }
-  }
-  if (style) {
-    element.attributes.style = style;
-    element.style = style;
-    element.declarations = properties;
-  } else {
-    delete element.attributes.style;
-    delete element.style;
-    delete element.declarations;
-  }
-}
diff --git a/lib/docdata.js b/lib/docdata.js
index 3ce8290..3cb99e1 100644
--- a/lib/docdata.js
+++ b/lib/docdata.js
@@ -12,7 +12,6 @@ import { CSSParseError } from './css.js';
 import { cssPropToString, getStyleDeclarations } from './css-tools.js';
 
 /**
- * @typedef {import('../lib/types.js').XastElement} XastElement
  * @typedef {import('../lib/types.js').XastParent} XastParent
  * @typedef {import('../lib/types.js').XastRoot} XastRoot
  */
@@ -36,7 +35,7 @@ export class StyleData {
   #referencedClasses;
 
   /**
-   * @param {XastElement[]} styleElements
+   * @param {import('../lib/types.js').XastElement[]} styleElements
    * @param {CSSRuleSet[]} ruleSets
    */
   constructor(styleElements, ruleSets) {
@@ -178,7 +177,7 @@ export class StyleData {
   }
 
   /**
-   * @param {XastElement} element
+   * @param {import('../lib/types.js').XastElement} element
    * @param {{element:XastParent,styles?:Map<string,string|null>}[]} parentInfo
    * @param {CSSDeclarationMap} [declarations]
    * @returns {Map<string,string|null>}
@@ -245,7 +244,7 @@ export class StyleData {
   }
 
   /**
-   * @param {XastElement} element
+   * @param {import('../lib/types.js').XastElement} element
    */
   getMatchingRules(element) {
     const rules = [];
@@ -306,6 +305,19 @@ export class StyleData {
     return this.getReferencedClasses().has(className);
   }
 
+  /**
+   * @param {string} id
+   * @returns {boolean}
+   */
+  hasIdSelector(id) {
+    for (const ruleSet of this.#ruleSets) {
+      if (ruleSet.hasIdSelector(id)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   /**
    * @param {CSSFeatures[]} features
    */
@@ -333,7 +345,7 @@ export class StyleData {
 
   mergeStyles() {
     /**
-     * @param {XastElement} element
+     * @param {import('../lib/types.js').XastElement} element
      */
     function gatherCSS(element) {
       let css = getCSS(element);
@@ -486,7 +498,7 @@ class DocData {
 }
 
 /**
- * @param {XastElement} styleElement
+ * @param {import('../lib/types.js').XastElement} styleElement
  */
 function getCSS(styleElement) {
   let css = '';
@@ -499,7 +511,7 @@ function getCSS(styleElement) {
 }
 
 /**
- * @param {XastElement} styleElement
+ * @param {import('../lib/types.js').XastElement} styleElement
  */
 function getRuleSets(styleElement) {
   /** @type {CSSRuleSet[]} */
@@ -537,11 +549,11 @@ function getRuleSets(styleElement) {
  * @param {XastRoot} root
  */
 export const getDocData = (root) => {
-  /** @type {XastElement[]} */
+  /** @type {import('../lib/types.js').XastElement[]} */
   const styleElements = [];
   /** @type {CSSRuleSet[]} */
   const ruleSets = [];
-  /** @type {Map<XastElement, XastParent>} */
+  /** @type {Map<import('../lib/types.js').XastElement, XastParent>} */
   const parents = new Map();
   let styleError = false;
   let hasAnimations = false;
diff --git a/lib/svgo/tools.js b/lib/svgo/tools.js
index c3b7178..f9e43e2 100644
--- a/lib/svgo/tools.js
+++ b/lib/svgo/tools.js
@@ -527,6 +527,45 @@ export function updateReferencedDeclarationIds(decls, idMap) {
   }
 }
 
+/**
+ * @param {import('../types.js').XastElement} element
+ * @param {string} attName
+ * @param {Map<string,string>} idMap
+ */
+export function updateReferencedId(element, attName, idMap) {
+  if (attName === 'style') {
+    updateReferencedStyleId(element, idMap);
+    return;
+  }
+
+  const attValue = element.attributes[attName];
+  const ids = getReferencedIdsInAttribute(attName, attValue);
+  if (ids.length !== 1) {
+    throw new Error();
+  }
+  const newId = idMap.get(ids[0].id);
+  if (newId === undefined) {
+    throw new Error();
+  }
+  element.attributes[attName] = attValue.replace(
+    '#' + ids[0].literalString,
+    '#' + newId,
+  );
+}
+
+/**
+ * @param {import('../types.js').XastElement} element
+ * @param {Map<string,string>} idMap
+ */
+function updateReferencedStyleId(element, idMap) {
+  const decls = getStyleDeclarations(element);
+  if (decls === undefined) {
+    throw new Error();
+  }
+  updateReferencedDeclarationIds(decls, idMap);
+  writeStyleAttribute(element, decls);
+}
+
 /**
  * @param {string} attribute
  * @param {string} value
@@ -584,3 +623,29 @@ export const toFixed = (num, precision) => {
   const pow = 10 ** precision;
   return Math.round(num * pow) / pow;
 };
+
+/**
+ * @param {import('../types.js').XastElement&{style?:string,declarations?:import('../types.js').CSSDeclarationMap}} element
+ * @param {import('../types.js').CSSDeclarationMap} properties
+ */
+export function writeStyleAttribute(element, properties) {
+  let style = '';
+  for (const [p, decValue] of properties.entries()) {
+    if (style !== '') {
+      style += ';';
+    }
+    style += `${p}:${decValue.value}`;
+    if (decValue.important) {
+      style += '!important';
+    }
+  }
+  if (style) {
+    element.attributes.style = style;
+    element.style = style;
+    element.declarations = properties;
+  } else {
+    delete element.attributes.style;
+    delete element.style;
+    delete element.declarations;
+  }
+}
diff --git a/lib/types.d.ts b/lib/types.d.ts
index cac0b49..749dbb3 100644
--- a/lib/types.d.ts
+++ b/lib/types.d.ts
@@ -131,6 +131,7 @@ export class StyleData {
   getReferencedIds(): Map<string, CSSRule[]>;
   hasAttributeSelector(attName?: string): boolean;
   hasClassReference(className: string): boolean;
+  hasIdSelector(id: string): boolean;
   hasOnlyFeatures(features: CSSFeatures[]): boolean;
   hasStyles(): boolean;
   mergeStyles(): void;
diff --git a/plugins/cleanupIds.js b/plugins/cleanupIds.js
index f3a5717..85d4e8d 100644
--- a/plugins/cleanupIds.js
+++ b/plugins/cleanupIds.js
@@ -1,11 +1,8 @@
-import { getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import {
   generateId,
-  getReferencedIdsInAttribute,
   recordReferencedIds,
   SVGOError,
-  updateReferencedDeclarationIds,
+  updateReferencedId,
 } from '../lib/svgo/tools.js';
 import { visitSkip } from '../lib/xast.js';
 import { elemsGroups } from './_collections.js';
@@ -13,45 +10,6 @@ import { elemsGroups } from './_collections.js';
 export const name = 'cleanupIds';
 export const description = 'removes unused IDs and minifies used';
 
-/**
- * @param {import('../lib/types.js').XastElement} element
- * @param {string} attName
- * @param {Map<string,string>} idMap
- */
-function updateReferencedId(element, attName, idMap) {
-  if (attName === 'style') {
-    updateReferencedStyleId(element, idMap);
-    return;
-  }
-
-  const attValue = element.attributes[attName];
-  const ids = getReferencedIdsInAttribute(attName, attValue);
-  if (ids.length !== 1) {
-    throw new Error();
-  }
-  const newId = idMap.get(ids[0].id);
-  if (newId === undefined) {
-    throw new Error();
-  }
-  element.attributes[attName] = attValue.replace(
-    '#' + ids[0].literalString,
-    '#' + newId,
-  );
-}
-
-/**
- * @param {import('../lib/types.js').XastElement} element
- * @param {Map<string,string>} idMap
- */
-function updateReferencedStyleId(element, idMap) {
-  const decls = getStyleDeclarations(element);
-  if (decls === undefined) {
-    throw new Error();
-  }
-  updateReferencedDeclarationIds(decls, idMap);
-  writeStyleAttribute(element, decls);
-}
-
 /**
  * Remove unused and minify used IDs
  *
diff --git a/plugins/cleanupStyleAttributes.js b/plugins/cleanupStyleAttributes.js
index 9a31e57..59b7817 100644
--- a/plugins/cleanupStyleAttributes.js
+++ b/plugins/cleanupStyleAttributes.js
@@ -1,6 +1,6 @@
 import { getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import { LengthOrPctValue } from '../lib/lengthOrPct.js';
+import { writeStyleAttribute } from '../lib/svgo/tools.js';
 import { visitSkip } from '../lib/xast.js';
 import {
   elemsGroups,
diff --git a/plugins/cleanupTextElements.js b/plugins/cleanupTextElements.js
index a709ddf..0ba7c61 100644
--- a/plugins/cleanupTextElements.js
+++ b/plugins/cleanupTextElements.js
@@ -1,5 +1,5 @@
 import { getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
+import { writeStyleAttribute } from '../lib/svgo/tools.js';
 
 export const name = 'cleanupTextElements';
 export const description = 'simplify <text> elements and content';
diff --git a/plugins/createGroups.js b/plugins/createGroups.js
index b3e1665..8ad39e9 100644
--- a/plugins/createGroups.js
+++ b/plugins/createGroups.js
@@ -1,8 +1,7 @@
 import { cssPropToString, getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import { svgSetAttValue } from '../lib/svg-parse-att.js';
 import { cssTransformToSVGAtt } from '../lib/svg-to-css.js';
-import { getHrefId } from '../lib/svgo/tools.js';
+import { getHrefId, writeStyleAttribute } from '../lib/svgo/tools.js';
 import { getInheritableProperties } from './_styles.js';
 
 export const name = 'createGroups';
diff --git a/plugins/inlineStyles.js b/plugins/inlineStyles.js
index 1a32407..4749c37 100644
--- a/plugins/inlineStyles.js
+++ b/plugins/inlineStyles.js
@@ -1,11 +1,10 @@
-import { writeStyleAttribute } from '../lib/css.js';
-
 /**
- * @typedef {import('../lib/types.js').XastElement} XastElement
  * @typedef {import('../lib/types.js').XastParent} XastParent
  * @typedef {import('../lib/types.js').CSSRule} CSSRule
  */
 
+import { writeStyleAttribute } from '../lib/svgo/tools.js';
+
 export const name = 'inlineStyles';
 export const description =
   'Move properties in <style> elements to style attributes';
@@ -23,14 +22,14 @@ export const fn = (root, params, info) => {
     return;
   }
 
-  /** @type {Map<CSSRule,XastElement[]>} */
+  /** @type {Map<CSSRule,import('../lib/types.js').XastElement[]>} */
   const elementsPerRule = new Map();
-  /** @type {Map<XastElement,CSSRule[]>} */
+  /** @type {Map<import('../lib/types.js').XastElement,CSSRule[]>} */
   const rulesPerElement = new Map();
 
   /**
    * @param {CSSRule} rule
-   * @param {XastElement} element
+   * @param {import('../lib/types.js').XastElement} element
    */
   function addElementToRule(rule, element) {
     if (rule.isInMediaQuery() || rule.hasPseudos()) {
@@ -47,7 +46,7 @@ export const fn = (root, params, info) => {
 
   /**
    * @param {CSSRule} rule
-   * @param {XastElement} element
+   * @param {import('../lib/types.js').XastElement} element
    */
   function addRuleToElement(rule, element) {
     const rules = rulesPerElement.get(element);
diff --git a/plugins/inlineUse.js b/plugins/inlineUse.js
index 6294e53..9b5fe8a 100644
--- a/plugins/inlineUse.js
+++ b/plugins/inlineUse.js
@@ -1,6 +1,9 @@
-import { writeStyleAttribute } from '../lib/css.js';
 import { cssTransformToSVGAtt } from '../lib/svg-to-css.js';
-import { getHrefId, getReferencedIds } from '../lib/svgo/tools.js';
+import {
+  getHrefId,
+  getReferencedIds,
+  writeStyleAttribute,
+} from '../lib/svgo/tools.js';
 import { getPresentationProperties } from './_styles.js';
 
 export const name = 'inlineUse';
diff --git a/plugins/mergeGradients.js b/plugins/mergeGradients.js
new file mode 100644
index 0000000..2f2d0ec
--- /dev/null
+++ b/plugins/mergeGradients.js
@@ -0,0 +1,136 @@
+import {
+  addChildToDelete,
+  deleteChildren,
+  recordReferencedIds,
+  updateReferencedId,
+} from '../lib/svgo/tools.js';
+
+export const name = 'mergeGradients';
+export const description = 'merge identical gradients';
+
+/**
+ * @type {import('./plugins-types.js').Plugin<'mergeGradients'>};
+ */
+export const fn = (root, params, info) => {
+  const styleData = info.docData.getStyles();
+  if (info.docData.hasScripts() || styleData === null) {
+    return;
+  }
+
+  // Map gradient to id.
+  /** @type {Map<string,string>} */
+  const uniqueGradients = new Map();
+
+  // Map unique gradient id to duplicate elements.
+  /** @type {import('../lib/types.js').XastElement[]} */
+  const duplicateGradients = [];
+
+  /** @type {import('../lib/svgo/tools.js').IdReferenceMap} */
+  const referencedIds = new Map();
+
+  /** @type {Map<string,string>} */
+  const idMap = new Map();
+
+  return {
+    element: {
+      enter: (element) => {
+        // Record all referenced ids.
+        recordReferencedIds(element, referencedIds);
+
+        switch (element.name) {
+          case 'linearGradient':
+          case 'radialGradient':
+            break;
+          default:
+            return;
+        }
+
+        const gradientId = element.attributes.id;
+        if (!gradientId) {
+          return;
+        }
+
+        if (styleData.hasIdSelector(gradientId)) {
+          // Don't merge gradients that are referenced by a selector.
+          return;
+        }
+
+        const key = getGradientKey(element);
+        if (!key) {
+          return;
+        }
+
+        const uniqueId = uniqueGradients.get(key);
+        if (uniqueId) {
+          duplicateGradients.push(element);
+          idMap.set(gradientId, uniqueId);
+        } else {
+          uniqueGradients.set(key, gradientId);
+        }
+      },
+    },
+    root: {
+      exit: () => {
+        const childrenToDelete = new Map();
+
+        // Merge any duplicates.
+        for (const duplicate of duplicateGradients) {
+          // Update all references.
+
+          addChildToDelete(childrenToDelete, duplicate);
+          const dupId = duplicate.attributes.id;
+          const dupReferencingEls = referencedIds.get(dupId);
+          if (!dupReferencingEls) {
+            continue;
+          }
+          for (const dupReferencingEl of dupReferencingEls) {
+            updateReferencedId(
+              dupReferencingEl.referencingEl,
+              dupReferencingEl.referencingAtt,
+              idMap,
+            );
+          }
+        }
+
+        // Update any ids referenced by <style> properties.
+        styleData.updateReferencedIds(styleData.getReferencedIds(), idMap);
+
+        // Delete merged nodes.
+        deleteChildren(childrenToDelete);
+      },
+    },
+  };
+};
+
+/**
+ * @param {import('../lib/types.js').XastElement} element
+ * @returns {string|undefined}
+ */
+function getGradientKey(element) {
+  /** @type {string[]} */
+  const parts = [];
+
+  /**
+   * @param {import('../lib/types.js').XastElement} element
+   * @param {boolean} excludeId
+   */
+  function addParts(element, excludeId) {
+    parts.push(element.name);
+    for (const [attName, attVal] of Object.entries(element.attributes)) {
+      if (excludeId && attName === 'id') {
+        continue;
+      }
+      parts.push(`${attName}:${attVal}`);
+    }
+  }
+
+  addParts(element, true);
+
+  for (const child of element.children) {
+    if (child.type !== 'element' || child.name !== 'stop') {
+      return;
+    }
+    addParts(child, false);
+  }
+  return parts.join();
+}
diff --git a/plugins/minifyColors.js b/plugins/minifyColors.js
index a207c42..2e6ed0e 100644
--- a/plugins/minifyColors.js
+++ b/plugins/minifyColors.js
@@ -1,7 +1,7 @@
 import { ColorValue } from '../lib/color.js';
 import { getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import { svgSetAttValue } from '../lib/svg-parse-att.js';
+import { writeStyleAttribute } from '../lib/svgo/tools.js';
 
 export const name = 'minifyColors';
 export const description =
diff --git a/plugins/minifyGradients.js b/plugins/minifyGradients.js
index 35071bd..29aa2a6 100644
--- a/plugins/minifyGradients.js
+++ b/plugins/minifyGradients.js
@@ -1,5 +1,4 @@
 import { cssPropToString, getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import { StopOffsetValue } from '../lib/stop-offset.js';
 import { svgSetAttValue } from '../lib/svg-parse-att.js';
 import { cssTransformToSVGAtt } from '../lib/svg-to-css.js';
@@ -7,6 +6,7 @@ import {
   getReferencedIdInStyleProperty,
   recordReferencedIds,
   SVGOError,
+  writeStyleAttribute,
 } from '../lib/svgo/tools.js';
 
 export const name = 'minifyGradients';
diff --git a/plugins/moveElemsStylesToGroup.js b/plugins/moveElemsStylesToGroup.js
index c81bdcc..364af7c 100644
--- a/plugins/moveElemsStylesToGroup.js
+++ b/plugins/moveElemsStylesToGroup.js
@@ -1,6 +1,6 @@
 import { cssPropToString, getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import { cssTransformToSVGAtt } from '../lib/svg-to-css.js';
+import { writeStyleAttribute } from '../lib/svgo/tools.js';
 import { getInheritableProperties, TRANSFORM_PROP_NAMES } from './_styles.js';
 
 export const name = 'moveElemsStylesToGroup';
diff --git a/plugins/plugins-types.d.ts b/plugins/plugins-types.d.ts
index a651ba1..4c9a8bf 100644
--- a/plugins/plugins-types.d.ts
+++ b/plugins/plugins-types.d.ts
@@ -75,6 +75,7 @@ type DefaultPlugins = {
      */
     usePseudos?: string[];
   };
+  mergeGradients: void;
   mergePaths: {
     force?: boolean;
     floatPrecision?: number;
diff --git a/plugins/preset-default.js b/plugins/preset-default.js
index 50b8d17..53c4993 100644
--- a/plugins/preset-default.js
+++ b/plugins/preset-default.js
@@ -9,6 +9,7 @@ import * as convertEllipseToCircle from './convertEllipseToCircle.js';
 import * as convertShapeToPath from './convertShapeToPath.js';
 import * as createGroups from './createGroups.js';
 import * as inlineStyles from './inlineStyles.js';
+import * as mergeGradients from './mergeGradients.js';
 import * as minifyColors from './minifyColors.js';
 import * as minifyGradients from './minifyGradients.js';
 import * as minifyPathData from './minifyPathData.js';
@@ -54,6 +55,7 @@ const presetDefault = createPreset({
     moveElemsStylesToGroup,
     convertShapeToPath,
     minifyPathData,
+    mergeGradients,
     removeEmptyContainers,
     removeUnusedNS,
     createGroups,
diff --git a/plugins/preset-next.js b/plugins/preset-next.js
index a565ce2..0bd4b13 100644
--- a/plugins/preset-next.js
+++ b/plugins/preset-next.js
@@ -9,6 +9,7 @@ import * as convertEllipseToCircle from './convertEllipseToCircle.js';
 import * as convertShapeToPath from './convertShapeToPath.js';
 import * as createGroups from './createGroups.js';
 import * as inlineStyles from './inlineStyles.js';
+import * as mergeGradients from './mergeGradients.js';
 import * as minifyColors from './minifyColors.js';
 import * as minifyGradients from './minifyGradients.js';
 import * as minifyPathData from './minifyPathData.js';
@@ -54,6 +55,7 @@ const presetNext = createPreset({
     moveElemsStylesToGroup,
     convertShapeToPath,
     minifyPathData,
+    mergeGradients,
     removeEmptyContainers,
     removeUnusedNS,
     createGroups,
diff --git a/plugins/removeUnknownsAndDefaults.js b/plugins/removeUnknownsAndDefaults.js
index 313c578..bce3ea8 100644
--- a/plugins/removeUnknownsAndDefaults.js
+++ b/plugins/removeUnknownsAndDefaults.js
@@ -6,9 +6,8 @@ import {
   inheritableAttrs,
 } from './_collections.js';
 import { visitSkip, detachNodeFromParent } from '../lib/xast.js';
-import { getHrefId } from '../lib/svgo/tools.js';
+import { getHrefId, writeStyleAttribute } from '../lib/svgo/tools.js';
 import { getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 
 export const name = 'removeUnknownsAndDefaults';
 export const description =
diff --git a/plugins/round.js b/plugins/round.js
index 4481b85..923305d 100644
--- a/plugins/round.js
+++ b/plugins/round.js
@@ -1,6 +1,5 @@
 import { ColorValue } from '../lib/color.js';
 import { getStyleDeclarations } from '../lib/css-tools.js';
-import { writeStyleAttribute } from '../lib/css.js';
 import { LengthValue } from '../lib/length.js';
 import { OpacityValue } from '../lib/opacity.js';
 import { parsePathCommands, stringifyPathCommands } from '../lib/pathutils.js';
@@ -10,7 +9,7 @@ import {
   svgSetAttValue,
   SVGTransformValue,
 } from '../lib/svg-parse-att.js';
-import { toFixed } from '../lib/svgo/tools.js';
+import { toFixed, writeStyleAttribute } from '../lib/svgo/tools.js';
 
 export const name = 'round';
 export const description = 'Round numbers to fewer decimal digits';
diff --git a/test/plugins/mergeGradients.01.svg.txt b/test/plugins/mergeGradients.01.svg.txt
new file mode 100644
index 0000000..91c2533
--- /dev/null
+++ b/test/plugins/mergeGradients.01.svg.txt
@@ -0,0 +1,31 @@
+Merge identical gradients.
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30">
+  <defs>
+    <linearGradient id="a">
+      <stop style="stop-color:#aaa"/>
+      <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+    </linearGradient>
+    <linearGradient id="b">
+      <stop style="stop-color:#aaa"/>
+      <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+    </linearGradient>
+  </defs>
+  <rect width="20" height="10" fill="url(#a)"/>
+  <rect y="15" width="20" height="10" fill="url(#b)"/>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30">
+    <defs>
+        <linearGradient id="a">
+            <stop style="stop-color:#aaa"/>
+            <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+        </linearGradient>
+    </defs>
+    <rect width="20" height="10" fill="url(#a)"/>
+    <rect y="15" width="20" height="10" fill="url(#a)"/>
+</svg>
diff --git a/test/plugins/mergeGradients.02.svg.txt b/test/plugins/mergeGradients.02.svg.txt
new file mode 100644
index 0000000..52eda23
--- /dev/null
+++ b/test/plugins/mergeGradients.02.svg.txt
@@ -0,0 +1,39 @@
+Don't merge gradients that are referenced in a <style> selector.
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30">
+  <style>
+      #b stop {stop-opacity:.5}
+  </style>
+  <defs>
+    <linearGradient id="a">
+      <stop style="stop-color:#aaa"/>
+      <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+    </linearGradient>
+    <linearGradient id="b">
+      <stop style="stop-color:#aaa"/>
+      <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+    </linearGradient>
+  </defs>
+  <rect width="20" height="10" fill="url(#a)"/>
+  <rect y="15" width="20" height="10" fill="url(#b)"/>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30">
+    <style>#b stop{stop-opacity:.5}</style>
+    <defs>
+        <linearGradient id="a">
+            <stop style="stop-color:#aaa"/>
+            <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+        </linearGradient>
+        <linearGradient id="b">
+            <stop style="stop-color:#aaa"/>
+            <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+        </linearGradient>
+    </defs>
+    <rect width="20" height="10" fill="url(#a)"/>
+    <rect y="15" width="20" height="10" fill="url(#b)"/>
+</svg>
diff --git a/test/plugins/mergeGradients.03.svg.txt b/test/plugins/mergeGradients.03.svg.txt
new file mode 100644
index 0000000..051b10a
--- /dev/null
+++ b/test/plugins/mergeGradients.03.svg.txt
@@ -0,0 +1,33 @@
+Merge gradients that are referenced in a <style> property.
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30">
+  <style>#c{fill:url(#b)}</style>
+  <defs>
+    <linearGradient id="a">
+      <stop style="stop-color:#aaa"/>
+      <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+    </linearGradient>
+    <linearGradient id="b">
+      <stop style="stop-color:#aaa"/>
+      <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+    </linearGradient>
+  </defs>
+  <rect width="20" height="10" fill="url(#a)"/>
+  <rect id="c" y="15" width="20" height="10"/>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30">
+    <style>#c{fill:url(#a)}</style>
+    <defs>
+        <linearGradient id="a">
+            <stop style="stop-color:#aaa"/>
+            <stop style="stop-color:#aaa;stop-opacity:0" offset="1"/>
+        </linearGradient>
+    </defs>
+    <rect width="20" height="10" fill="url(#a)"/>
+    <rect id="c" y="15" width="20" height="10"/>
+</svg>