diff --git a/crates/wac-graph/src/encoding.rs b/crates/wac-graph/src/encoding.rs
index 4a1c172..a290387 100644
--- a/crates/wac-graph/src/encoding.rs
+++ b/crates/wac-graph/src/encoding.rs
@@ -311,6 +311,7 @@ impl<'a> TypeEncoder<'a> {
             DefinedType::Tuple(types) => self.tuple(state, types),
             DefinedType::List(ty) => self.list(state, *ty),
             DefinedType::FixedSizeList(ty, elements) => self.fixed_size_list(state, *ty, *elements),
+            DefinedType::Map(key, value) => self.map(state, *key, *value),
             DefinedType::Option(ty) => self.option(state, *ty),
             DefinedType::Result { ok, err } => self.result(state, *ok, *err),
             DefinedType::Variant(v) => self.variant(state, v),
@@ -640,6 +641,14 @@ impl<'a> TypeEncoder<'a> {
         index
     }
 
+    fn map(&self, state: &mut State, key: ValueType, value: ValueType) -> u32 {
+        let key = self.value_type(state, key);
+        let value = self.value_type(state, value);
+        let index = state.current.encodable.type_count();
+        state.current.encodable.ty().defined_type().map(key, value);
+        index
+    }
+
     fn fixed_size_list(&self, state: &mut State, ty: ValueType, elements: u32) -> u32 {
         let ty = self.value_type(state, ty);
         let index = state.current.encodable.type_count();
diff --git a/crates/wac-graph/tests/graphs/map-type-mismatch/error.txt b/crates/wac-graph/tests/graphs/map-type-mismatch/error.txt
new file mode 100644
index 0000000..ece8493
--- /dev/null
+++ b/crates/wac-graph/tests/graphs/map-type-mismatch/error.txt
@@ -0,0 +1,8 @@
+failed to add argument edge from source node 2 to target node 1 referenced in argument 0 for test case `map-type-mismatch`
+
+Caused by:
+    0: mismatched instantiation argument `test:foo/consume`
+    1: mismatched type for export `lookup`
+    2: mismatched type for function parameter `m`
+    3: mismatched type for map value
+    4: expected u64, found u32
diff --git a/crates/wac-graph/tests/graphs/map-type-mismatch/foo.wit b/crates/wac-graph/tests/graphs/map-type-mismatch/foo.wit
new file mode 100644
index 0000000..cc8ffb9
--- /dev/null
+++ b/crates/wac-graph/tests/graphs/map-type-mismatch/foo.wit
@@ -0,0 +1,14 @@
+package test:foo;
+
+interface produce {
+    lookup: func(m: map<string, u32>) -> u32;
+}
+
+interface consume {
+    lookup: func(m: map<string, u64>) -> u32;
+}
+
+world w {
+    import consume;
+    export produce;
+}
diff --git a/crates/wac-graph/tests/graphs/map-type-mismatch/graph.json b/crates/wac-graph/tests/graphs/map-type-mismatch/graph.json
new file mode 100644
index 0000000..d711012
--- /dev/null
+++ b/crates/wac-graph/tests/graphs/map-type-mismatch/graph.json
@@ -0,0 +1,30 @@
+{
+    "packages": [
+        {
+            "name": "test:foo",
+            "path": "foo.wit"
+        }
+    ],
+    "nodes": [
+        {
+            "type": "instantiation",
+            "package": 0
+        },
+        {
+            "type": "instantiation",
+            "package": 0
+        },
+        {
+            "type": "alias",
+            "source": 0,
+            "export": "test:foo/produce"
+        }
+    ],
+    "arguments": [
+        {
+            "source": 2,
+            "target": 1,
+            "name": "test:foo/consume"
+        }
+    ]
+}
\ No newline at end of file
diff --git a/crates/wac-graph/tests/graphs/map-types/encoded.wat b/crates/wac-graph/tests/graphs/map-types/encoded.wat
new file mode 100644
index 0000000..28754d2
--- /dev/null
+++ b/crates/wac-graph/tests/graphs/map-types/encoded.wat
@@ -0,0 +1,63 @@
+(component
+  (type (;0;)
+    (instance
+      (type (;0;) (map string string))
+      (export (;1;) "headers" (type (eq 0)))
+      (type (;2;) (map string u32))
+      (type (;3;) (option u32))
+      (type (;4;) (func (param "m" 2) (result 3)))
+      (export (;0;) "lookup" (func (type 4)))
+      (type (;5;) (list u8))
+      (type (;6;) (map string 5))
+      (type (;7;) (func (param "h" 1) (result 6)))
+      (export (;1;) "bundle" (func (type 7)))
+    )
+  )
+  (import "test:foo/i" (instance (;0;) (type 0)))
+  (type (;1;)
+    (component
+      (type (;0;)
+        (instance
+          (type (;0;) (map string string))
+          (export (;1;) "headers" (type (eq 0)))
+          (type (;2;) (map string u32))
+          (type (;3;) (option u32))
+          (type (;4;) (func (param "m" 2) (result 3)))
+          (export (;0;) "lookup" (func (type 4)))
+          (type (;5;) (list u8))
+          (type (;6;) (map string 5))
+          (type (;7;) (func (param "h" 1) (result 6)))
+          (export (;1;) "bundle" (func (type 7)))
+        )
+      )
+      (import "test:foo/i" (instance (;0;) (type 0)))
+      (type (;1;)
+        (instance
+          (type (;0;) (map string string))
+          (export (;1;) "headers" (type (eq 0)))
+          (type (;2;) (map string u32))
+          (type (;3;) (option u32))
+          (type (;4;) (func (param "m" 2) (result 3)))
+          (export (;0;) "lookup" (func (type 4)))
+          (type (;5;) (list u8))
+          (type (;6;) (map string 5))
+          (type (;7;) (func (param "h" 1) (result 6)))
+          (export (;1;) "bundle" (func (type 7)))
+        )
+      )
+      (export (;1;) "test:foo/i" (instance (type 1)))
+    )
+  )
+  (import "unlocked-dep=<test:foo>" (component (;0;) (type 1)))
+  (instance (;1;) (instantiate 0
+      (with "test:foo/i" (instance 0))
+    )
+  )
+  (alias export 1 "test:foo/i" (instance (;2;)))
+  (instance (;3;) (instantiate 0
+      (with "test:foo/i" (instance 2))
+    )
+  )
+  (alias export 3 "test:foo/i" (instance (;4;)))
+  (export (;5;) "test:foo/i" (instance 4))
+)
diff --git a/crates/wac-graph/tests/graphs/map-types/foo.wit b/crates/wac-graph/tests/graphs/map-types/foo.wit
new file mode 100644
index 0000000..d1d5136
--- /dev/null
+++ b/crates/wac-graph/tests/graphs/map-types/foo.wit
@@ -0,0 +1,12 @@
+package test:foo;
+
+interface i {
+    type headers = map<string, string>;
+    lookup: func(m: map<string, u32>) -> option<u32>;
+    bundle: func(h: headers) -> map<string, list<u8>>;
+}
+
+world w {
+    import i;
+    export i;
+}
diff --git a/crates/wac-graph/tests/graphs/map-types/graph.json b/crates/wac-graph/tests/graphs/map-types/graph.json
new file mode 100644
index 0000000..1870b2b
--- /dev/null
+++ b/crates/wac-graph/tests/graphs/map-types/graph.json
@@ -0,0 +1,41 @@
+{
+    "packages": [
+        {
+            "name": "test:foo",
+            "path": "foo.wit"
+        }
+    ],
+    "nodes": [
+        {
+            "type": "instantiation",
+            "package": 0
+        },
+        {
+            "type": "instantiation",
+            "package": 0
+        },
+        {
+            "type": "alias",
+            "source": 0,
+            "export": "test:foo/i"
+        },
+        {
+            "type": "alias",
+            "source": 1,
+            "export": "test:foo/i"
+        }
+    ],
+    "arguments": [
+        {
+            "source": 2,
+            "target": 1,
+            "name": "test:foo/i"
+        }
+    ],
+    "exports": [
+        {
+            "node": 3,
+            "name": "test:foo/i"
+        }
+    ]
+}
diff --git a/crates/wac-types/src/aggregator.rs b/crates/wac-types/src/aggregator.rs
index 1b14421..2cb6131 100644
--- a/crates/wac-types/src/aggregator.rs
+++ b/crates/wac-types/src/aggregator.rs
@@ -871,6 +871,10 @@ impl TypeAggregator {
             DefinedType::FixedSizeList(ty, elements) => {
                 DefinedType::FixedSizeList(self.remap_value_type(types, *ty, checker)?, *elements)
             }
+            DefinedType::Map(key, value) => DefinedType::Map(
+                self.remap_value_type(types, *key, checker)?,
+                self.remap_value_type(types, *value, checker)?,
+            ),
             DefinedType::Option(ty) => {
                 DefinedType::Option(self.remap_value_type(types, *ty, checker)?)
             }
diff --git a/crates/wac-types/src/checker.rs b/crates/wac-types/src/checker.rs
index 9ce5432..0592808 100644
--- a/crates/wac-types/src/checker.rs
+++ b/crates/wac-types/src/checker.rs
@@ -583,6 +583,12 @@ impl<'a> SubtypeChecker<'a> {
                 self.value_type(*a, at, *b, bt)
                     .context("mismatched type for fixed size list element")
             }
+            (DefinedType::Map(akey, avalue), DefinedType::Map(bkey, bvalue)) => {
+                self.value_type(*akey, at, *bkey, bt)
+                    .context("mismatched type for map key")?;
+                self.value_type(*avalue, at, *bvalue, bt)
+                    .context("mismatched type for map value")
+            }
             (DefinedType::Future(a), DefinedType::Future(b)) => self
                 .payload(*a, at, *b, bt)
                 .context("mismatched type for future payload"),
@@ -616,6 +622,7 @@ impl<'a> SubtypeChecker<'a> {
             (DefinedType::Tuple(_), _)
             | (DefinedType::List(_), _)
             | (DefinedType::FixedSizeList(_, _), _)
+            | (DefinedType::Map(_, _), _)
             | (DefinedType::Option(_), _)
             | (DefinedType::Result { .. }, _)
             | (DefinedType::Variant(_), _)
diff --git a/crates/wac-types/src/component.rs b/crates/wac-types/src/component.rs
index 126f29a..47a1d05 100644
--- a/crates/wac-types/src/component.rs
+++ b/crates/wac-types/src/component.rs
@@ -661,6 +661,8 @@ pub enum DefinedType {
     List(ValueType),
     /// A fixed size array
     FixedSizeList(ValueType, u32),
+    /// A map type.
+    Map(ValueType, ValueType),
     /// An option type.
     Option(ValueType),
     /// A result type.
@@ -692,6 +694,7 @@ impl DefinedType {
         match self {
             Self::Tuple(tys) => tys.iter().any(|ty| ty.contains_borrow(types)),
             Self::List(ty) | Self::FixedSizeList(ty, _) => ty.contains_borrow(types),
+            Self::Map(key, value) => key.contains_borrow(types) || value.contains_borrow(types),
             Self::Option(ty) => ty.contains_borrow(types),
             Self::Result { ok, err } => {
                 ok.map(|ty| ty.contains_borrow(types)).unwrap_or(false)
@@ -726,6 +729,10 @@ impl DefinedType {
             DefinedType::List(ty) | DefinedType::Option(ty) | DefinedType::FixedSizeList(ty, _) => {
                 ty._visit_defined_types(types, visitor, false)
             }
+            DefinedType::Map(key, value) => {
+                key._visit_defined_types(types, visitor, false)?;
+                value._visit_defined_types(types, visitor, false)
+            }
             DefinedType::Result { ok, err } => {
                 if let Some(ty) = ok.as_ref() {
                     ty._visit_defined_types(types, visitor, false)?;
@@ -768,6 +775,7 @@ impl DefinedType {
             Self::Tuple(_) => "tuple",
             Self::List(_) => "list",
             Self::FixedSizeList(_, _) => "list<,N>",
+            Self::Map(_, _) => "map",
             Self::Option(_) => "option",
             Self::Result { .. } => "result",
             Self::Variant(_) => "variant",
diff --git a/crates/wac-types/src/package.rs b/crates/wac-types/src/package.rs
index f5590ea..0ebdb94 100644
--- a/crates/wac-types/src/package.rs
+++ b/crates/wac-types/src/package.rs
@@ -773,8 +773,13 @@ impl<'a> TypeConverter<'a> {
                         .add_defined_type(DefinedType::FixedSizeList(ty, *length)),
                 )
             }
-            wasm::ComponentDefinedType::Map { .. } => {
-                bail!("ComponentDefinedType::Map is not yet supported");
+            wasm::ComponentDefinedType::Map { key, value, .. } => {
+                let key_ty = self.component_val_type(*key)?;
+                let value_ty = self.component_val_type(*value)?;
+                ValueType::Defined(
+                    self.types
+                        .add_defined_type(DefinedType::Map(key_ty, value_ty)),
+                )
             }
         };