diff --git a/terraform/state.go b/terraform/state.go
index dea8fe961..ccb4b5737 100644
--- a/terraform/state.go
+++ b/terraform/state.go
@@ -100,6 +100,29 @@ func (s *State) ModuleByPath(path []string) *ModuleState {
 	return nil
 }
 
+// ModuleOrphans returns all the module orphans in this state by
+// returning their full paths. These paths can be used with ModuleByPath
+// to return the actual state.
+func (s *State) ModuleOrphans(path []string, c *config.Config) [][]string {
+	childrenKeys := make(map[string]struct{})
+	for _, m := range c.Modules {
+		childrenKeys[m.Name] = struct{}{}
+	}
+
+	// Go over the direct children and find any that aren't in our
+	// keys.
+	var orphans [][]string
+	for _, m := range s.Children(path) {
+		if _, ok := childrenKeys[m.Path[len(m.Path)-1]]; ok {
+			continue
+		}
+
+		orphans = append(orphans, m.Path)
+	}
+
+	return orphans
+}
+
 // RootModule returns the ModuleState for the root module
 func (s *State) RootModule() *ModuleState {
 	root := s.ModuleByPath(rootModulePath)
diff --git a/terraform/state_test.go b/terraform/state_test.go
index 7a5554651..f7889dc6d 100644
--- a/terraform/state_test.go
+++ b/terraform/state_test.go
@@ -59,6 +59,32 @@ func TestStateAddModule(t *testing.T) {
 	}
 }
 
+func TestStateModuleOrphans(t *testing.T) {
+	state := &State{
+		Modules: []*ModuleState{
+			&ModuleState{
+				Path: RootModulePath,
+			},
+			&ModuleState{
+				Path: []string{RootModuleName, "foo"},
+			},
+			&ModuleState{
+				Path: []string{RootModuleName, "bar"},
+			},
+		},
+	}
+
+	config := testModule(t, "state-module-orphans").Config()
+	actual := state.ModuleOrphans(RootModulePath, config)
+	expected := [][]string{
+		[]string{RootModuleName, "foo"},
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
 func TestInstanceState_MergeDiff(t *testing.T) {
 	is := InstanceState{
 		ID: "foo",
diff --git a/terraform/test-fixtures/state-module-orphans/bar/main.tf b/terraform/test-fixtures/state-module-orphans/bar/main.tf
new file mode 100644
index 000000000..c01ade299
--- /dev/null
+++ b/terraform/test-fixtures/state-module-orphans/bar/main.tf
@@ -0,0 +1 @@
+# Nothing
diff --git a/terraform/test-fixtures/state-module-orphans/main.tf b/terraform/test-fixtures/state-module-orphans/main.tf
new file mode 100644
index 000000000..f009f1924
--- /dev/null
+++ b/terraform/test-fixtures/state-module-orphans/main.tf
@@ -0,0 +1,3 @@
+module "bar" {
+    source = "./bar"
+}