diff --git a/README.md b/README.md
index 44e7efc..bc77333 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,7 @@ This package is fully typed with [TypeScript][].
 
 - [`FileSystem`](./src/interfaces/file-system.mts)
 - [`LoadTsconfigOptions`](./src/interfaces/options-load-tsconfig.mts)
+- [`ModuleResolutionHost`](./src/interfaces/host-module-resolution.mts)
 - [`ReadTsconfigOptions`](./src/interfaces/options-read-tsconfig.mts)
 - [`ResolvePathOptions`](./src/interfaces/options-resolve-path.mts)
 - [`ResolvedTsconfig`](./src/interfaces/options-resolve-path.mts)
diff --git a/src/interfaces/__tests__/host-module-resolution.spec-d.mts b/src/interfaces/__tests__/host-module-resolution.spec-d.mts
new file mode 100644
index 0000000..90ca64c
--- /dev/null
+++ b/src/interfaces/__tests__/host-module-resolution.spec-d.mts
@@ -0,0 +1,114 @@
+/**
+ * @file Type Tests - ModuleResolutionHost
+ * @module tsconfig-utils/interfaces/tests/unit-d/ModuleResolutionHost
+ */
+
+import type TestSubject from '#interfaces/host-module-resolution'
+import type { ModuleId } from '@flex-development/mlly'
+import type ts from 'typescript'
+
+describe('unit-d:interfaces/ModuleResolutionHost', () => {
+  it('should match ts.ModuleResolutionHost', () => {
+    expectTypeOf<TestSubject>().toMatchTypeOf<ts.ModuleResolutionHost>()
+  })
+
+  describe('directoryExists', () => {
+    type Subject = TestSubject['directoryExists']
+
+    it('should match [this: void]', () => {
+      expectTypeOf<Subject>().thisParameter.toEqualTypeOf<void>()
+    })
+
+    describe('parameters', () => {
+      it('should be callable with [ModuleId]', () => {
+        expectTypeOf<Subject>().parameters.toEqualTypeOf<[ModuleId]>()
+      })
+    })
+
+    describe('returns', () => {
+      it('should return boolean', () => {
+        expectTypeOf<Subject>().returns.toEqualTypeOf<boolean>()
+      })
+    })
+  })
+
+  describe('fileExists', () => {
+    type Subject = TestSubject['fileExists']
+
+    it('should match [this: void]', () => {
+      expectTypeOf<Subject>().thisParameter.toEqualTypeOf<void>()
+    })
+
+    describe('parameters', () => {
+      it('should be callable with [ModuleId]', () => {
+        expectTypeOf<Subject>().parameters.toEqualTypeOf<[ModuleId]>()
+      })
+    })
+
+    describe('returns', () => {
+      it('should return boolean', () => {
+        expectTypeOf<Subject>().returns.toEqualTypeOf<boolean>()
+      })
+    })
+  })
+
+  describe('getDirectories', () => {
+    type Subject = TestSubject['getDirectories']
+
+    it('should match [this: void]', () => {
+      expectTypeOf<Subject>().thisParameter.toEqualTypeOf<void>()
+    })
+
+    describe('parameters', () => {
+      it('should be callable with [ModuleId]', () => {
+        expectTypeOf<Subject>().parameters.toEqualTypeOf<[ModuleId]>()
+      })
+    })
+
+    describe('returns', () => {
+      it('should return string[]', () => {
+        expectTypeOf<Subject>().returns.toEqualTypeOf<string[]>()
+      })
+    })
+  })
+
+  describe('readFile', () => {
+    type Subject = TestSubject['readFile']
+
+    it('should match [this: void]', () => {
+      expectTypeOf<Subject>().thisParameter.toEqualTypeOf<void>()
+    })
+
+    describe('parameters', () => {
+      it('should be callable with [ModuleId]', () => {
+        expectTypeOf<Subject>().parameters.toEqualTypeOf<[ModuleId]>()
+      })
+    })
+
+    describe('returns', () => {
+      it('should return string | undefined', () => {
+        expectTypeOf<Subject>().returns.toEqualTypeOf<string | undefined>()
+      })
+    })
+  })
+
+  describe('realpath', () => {
+    type Subject = TestSubject['realpath']
+
+    it('should match [this: void]', () => {
+      expectTypeOf<Subject>().thisParameter.toEqualTypeOf<void>()
+    })
+
+    describe('parameters', () => {
+      it('should be callable with [ModuleId]', () => {
+        expectTypeOf<Subject>().parameters.toEqualTypeOf<[ModuleId]>()
+      })
+    })
+
+    describe('returns', () => {
+      it('should return string', () => {
+        expectTypeOf<Subject>().returns.toEqualTypeOf<string>()
+      })
+    })
+  })
+})
diff --git a/src/interfaces/host-module-resolution.mts b/src/interfaces/host-module-resolution.mts
new file mode 100644
index 0000000..8e722ab
--- /dev/null
+++ b/src/interfaces/host-module-resolution.mts
@@ -0,0 +1,101 @@
+/**
+ * @file Interfaces - ModuleResolutionHost
+ * @module tsconfig-utils/interfaces/ModuleResolutionHost
+ */
+
+import type { ModuleId } from '@flex-development/mlly'
+
+/**
+ * Module resolution host API.
+ *
+ * The module resolution host acts a bridge between the TypeScript compiler and
+ * the file system.
+ */
+interface ModuleResolutionHost {
+  /**
+   * Check if a directory exists at `id`.
+   *
+   * @see {@linkcode ModuleId}
+   *
+   * @this {void}
+   *
+   * @param {ModuleId} id
+   *  The module id to check
+   * @return {boolean}
+   *  `true` if directory exists at `id`, `false` otherwise
+   */
+  directoryExists(this: void, id: ModuleId): boolean
+
+  /**
+   * Check if a file exists at `id`.
+   *
+   * @see {@linkcode ModuleId}
+   *
+   * @this {void}
+   *
+   * @param {ModuleId} id
+   *  The module id to check
+   * @return {boolean}
+   *  `true` if file exists at `id`, `false` otherwise
+   */
+  fileExists(this: void, id: ModuleId): boolean
+
+  /**
+   * Get the path to current working directory.
+   *
+   * @this {void}
+   *
+   * @return {string}
+   *  Path to current working directory
+   */
+  getCurrentDirectory(this: void): string
+
+  /**
+   * Get a list of subdirectories.
+   *
+   * @see {@linkcode ModuleId}
+   *
+   * @this {void}
+   *
+   * @param {ModuleId} id
+   *  The directory path or URL to read
+   * @return {string[]}
+   *  List of subdirectory names
+   */
+  getDirectories(this: void, id: ModuleId): string[]
+
+  /**
+   * Get the contents of a file.
+   *
+   * @see {@linkcode ModuleId}
+   *
+   * @this {void}
+   *
+   * @param {ModuleId} id
+   *  Module id of file
+   * @return {Buffer | string}
+   *  File contents or `undefined` if file does not exist at `id`
+   */
+  readFile(this: void, id: ModuleId): string | undefined
+
+  /**
+   * Get the resolved pathname for `id`.
+   *
+   * @see {@linkcode ModuleId}
+   *
+   * @this {void}
+   *
+   * @param {ModuleId} id
+   *  The path or `file:` URL to handle
+   * @return {string}
+   *  Resolved pathname
+   */
+  realpath(this: void, id: ModuleId): string
+
+  /**
+   * Treat filenames as case-sensitive?
+   */
+  useCaseSensitiveFileNames?: ((this: void) => boolean) | boolean | undefined
+}
+
+export type { ModuleResolutionHost as default }
diff --git a/src/interfaces/index.mts b/src/interfaces/index.mts
index 4facc38..5e617c9 100644
--- a/src/interfaces/index.mts
+++ b/src/interfaces/index.mts
@@ -4,6 +4,9 @@
  */
 
 export type { default as FileSystem } from '#interfaces/file-system'
+export type {
+  default as ModuleResolutionHost
+} from '#interfaces/host-module-resolution'
 export type {
   default as LoadTsconfigOptions
 } from '#interfaces/options-load-tsconfig'