diff --git a/vyper/exceptions.py b/vyper/exceptions.py
index 3bde20356e6..2d9073e90ce 100644
--- a/vyper/exceptions.py
+++ b/vyper/exceptions.py
@@ -229,6 +229,10 @@ class CallViolation(VyperException):
     """Illegal function call."""
 
 
+class ImportCycle(VyperException):
+    """An import cycle"""
+
+
 class ImmutableViolation(VyperException):
     """Modifying an immutable variable, constant, or definition."""
 
diff --git a/vyper/semantics/analysis/module.py b/vyper/semantics/analysis/module.py
index edfb6bde8d4..4cb2e64c43d 100644
--- a/vyper/semantics/analysis/module.py
+++ b/vyper/semantics/analysis/module.py
@@ -34,7 +34,11 @@
 from vyper.semantics.types.utils import type_from_annotation
 
 
-def validate_semantics(module_ast: vy_ast.Module, input_bundle: InputBundle):
+def validate_semantics(module_ast, input_bundle):
+    return validate_semantics_r(module_ast, input_bundle, [])
+
+
+def validate_semantics_r(module_ast: vy_ast.Module, input_bundle: InputBundle, import_graph: list = None):
     """
     Analyze a Vyper module AST node, add all module-level objects to the
     namespace, type-check/validate semantics and annotate with type and analysis info
@@ -44,7 +48,7 @@ def validate_semantics(module_ast: vy_ast.Module, input_bundle: InputBundle):
 
     with namespace.enter_scope():
         namespace = get_namespace()
-        analyzer = ModuleAnalyzer(module_ast, input_bundle, namespace)
+        analyzer = ModuleAnalyzer(module_ast, input_bundle, namespace, import_graph)
         analyzer.analyze()
 
         vy_ast.expansion.expand_annotated_ast(module_ast)
@@ -85,14 +89,37 @@ def _find_cyclic_call(fn_t: ContractFunctionT, path: list = None):
 class ModuleAnalyzer(VyperNodeVisitorBase):
     scope_name = "module"
 
+    # class object
+    _ast_of: dict[FileInput, vy_ast.Module]
+
     def __init__(
-        self, module_node: vy_ast.Module, input_bundle: InputBundle, namespace: Namespace
+        self, module_node: vy_ast.Module, input_bundle: InputBundle, namespace: Namespace, import_graph: list
     ) -> None:
         self.ast = module_node
         self.input_bundle = input_bundle
         self.namespace = namespace
+        self.import_graph = import_graph
+
+        self.module_t = None
 
     def analyze(self) -> ModuleT:
+        # generate a `ModuleT` from the top-level node
+        # note: also validates unique method ids
+        if "type" in self.ast._metadata:
+            assert isinstance(self.ast._metadata["type"], ModuleT)
+            # we don't need to analyse again, skip out
+            self.module_t = self.ast._metadata["type"]
+            return self.module_t
+
+        else:
+            self.module_t = ModuleT(self.ast)
+            self.ast._metadata["type"] = self.module_t
+
+        if self.module_t in self.import_graph:
+            raise ImportCycle(" -> ".join(str(t) for t in self.import_graph + [self.module_t]))
+
+        self.import_graph.append(self.module_t)
+
         module_nodes = self.ast.body.copy()
         while module_nodes:
             count = len(module_nodes)
@@ -113,11 +140,6 @@ def analyze(self) -> ModuleT:
             if count == len(module_nodes):
                 err_list.raise_if_not_empty()
 
-        # generate a `ModuleT` from the top-level node
-        # note: also validates unique method ids
-        self.module_t = ModuleT(self.ast)
-        self.ast._metadata["type"] = self.module_t
-
         # attach namespace to the module for downstream use.
         _ns = Namespace()
         # note that we don't just copy the namespace because
@@ -127,6 +149,8 @@ def analyze(self) -> ModuleT:
 
         self.analyze_call_graph()
 
+        assert self.module_t == self.import_graph.pop()
+
     def analyze_call_graph(self):
         # get list of internal function calls made by each function
         function_defs = self.module_t.functions
@@ -157,6 +181,15 @@ def analyze_call_graph(self):
 
             _compute_reachable_set(fn_t)
 
+    @classmethod
+    def _ast_from_file(cls, file: FileInput):
+        if file not in cls._ast_of:
+            cls._ast_of[file] = vy_ast.parse_to_ast(
+                file.source_code, module_path=str(path_vy), module_name=alias
+            )
+
+        return cls._ast_of[file]
+
     def visit_ImplementsDecl(self, node):
         type_ = type_from_annotation(node.annotation)
         if not isinstance(type_, InterfaceT):
@@ -355,12 +388,10 @@ def _load_import(self, node: vy_ast.VyperNode, level: int, module_str: str, alia
             file = self.input_bundle.load_file(path_vy)
             assert isinstance(file, FileInput)  # mypy hint
 
-            # TODO share work if same file is imported
-            module_ast = vy_ast.parse_to_ast(
-                file.source_code, module_path=str(path_vy), module_name=alias
-            )
+            module_ast = self.__class__._ast_from_file(file)
+
             with override_global_namespace(Namespace()):
-                validate_semantics(module_ast, self.input_bundle)
+                validate_semantics_r(module_ast, self.input_bundle, import_graph=self._import_graph)
                 module_t = module_ast._metadata["type"]
 
                 return ModuleInfo(module_t, decl_node=node)