diff --git a/lib/src/default_submodule_store.rs b/lib/src/default_submodule_store.rs
new file mode 100644
index 000000000..243c22308
--- /dev/null
+++ b/lib/src/default_submodule_store.rs
@@ -0,0 +1,48 @@
+// Copyright 2023 The Jujutsu Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::path::{Path, PathBuf};
+
+use crate::submodule_store::SubmoduleStore;
+
+#[derive(Debug)]
+pub struct DefaultSubmoduleStore {
+    #[allow(dead_code)]
+    path: PathBuf,
+}
+
+impl DefaultSubmoduleStore {
+    /// Load an existing SubmoduleStore
+    pub fn load(store_path: &Path) -> Self {
+        DefaultSubmoduleStore {
+            path: store_path.to_path_buf(),
+        }
+    }
+
+    pub fn init(store_path: &Path) -> Self {
+        DefaultSubmoduleStore {
+            path: store_path.to_path_buf(),
+        }
+    }
+
+    pub fn name() -> &'static str {
+        "default"
+    }
+}
+
+impl SubmoduleStore for DefaultSubmoduleStore {
+    fn name(&self) -> &str {
+        DefaultSubmoduleStore::name()
+    }
+}
diff --git a/lib/src/lib.rs b/lib/src/lib.rs
index 31ba31ee3..70984f38c 100644
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@@ -25,6 +25,7 @@ pub mod dag_walk;
 pub mod default_index_store;
 pub mod default_revset_engine;
 pub mod default_revset_graph_iterator;
+pub mod default_submodule_store;
 pub mod diff;
 pub mod file_util;
 pub mod files;
@@ -53,6 +54,7 @@ pub mod simple_op_heads_store;
 pub mod simple_op_store;
 pub mod stacked_table;
 pub mod store;
+pub mod submodule_store;
 pub mod transaction;
 pub mod tree;
 pub mod tree_builder;
diff --git a/lib/src/repo.rs b/lib/src/repo.rs
index b0c1aab5d..ad8fcad4a 100644
--- a/lib/src/repo.rs
+++ b/lib/src/repo.rs
@@ -30,6 +30,7 @@ use crate::backend::{Backend, BackendError, BackendResult, ChangeId, CommitId, O
 use crate::commit::Commit;
 use crate::commit_builder::CommitBuilder;
 use crate::default_index_store::DefaultIndexStore;
+use crate::default_submodule_store::DefaultSubmoduleStore;
 use crate::git_backend::GitBackend;
 use crate::index::{HexPrefix, Index, IndexStore, MutableIndex, PrefixResolution, ReadonlyIndex};
 use crate::local_backend::LocalBackend;
@@ -43,6 +44,7 @@ use crate::settings::{RepoSettings, UserSettings};
 use crate::simple_op_heads_store::SimpleOpHeadsStore;
 use crate::simple_op_store::SimpleOpStore;
 use crate::store::Store;
+use crate::submodule_store::SubmoduleStore;
 use crate::transaction::Transaction;
 use crate::view::{RefName, View};
 use crate::{backend, dag_walk, op_store};
@@ -56,6 +58,8 @@ pub trait Repo {
 
     fn view(&self) -> &View;
 
+    fn submodule_store(&self) -> &Arc<dyn SubmoduleStore>;
+
     fn resolve_change_id(&self, change_id: &ChangeId) -> Option<Vec<CommitId>> {
         // Replace this if we added more efficient lookup method.
         let prefix = HexPrefix::from_bytes(change_id.as_bytes());
@@ -79,6 +83,7 @@ pub struct ReadonlyRepo {
     operation: Operation,
     settings: RepoSettings,
     index_store: Arc<dyn IndexStore>,
+    submodule_store: Arc<dyn SubmoduleStore>,
     index: OnceCell<Pin<Box<dyn ReadonlyIndex>>>,
     // Declared after `change_id_index` since it must outlive it on drop.
     change_id_index: OnceCell<Box<dyn ChangeIdIndex>>,
@@ -111,6 +116,10 @@ impl ReadonlyRepo {
         |store_path| Box::new(DefaultIndexStore::init(store_path))
     }
 
+    pub fn default_submodule_store_factory() -> impl FnOnce(&Path) -> Box<dyn SubmoduleStore> {
+        |store_path| Box::new(DefaultSubmoduleStore::init(store_path))
+    }
+
     pub fn init(
         user_settings: &UserSettings,
         repo_path: &Path,
@@ -118,6 +127,7 @@ impl ReadonlyRepo {
         op_store_factory: impl FnOnce(&Path) -> Box<dyn OpStore>,
         op_heads_store_factory: impl FnOnce(&Path) -> Box<dyn OpHeadsStore>,
         index_store_factory: impl FnOnce(&Path) -> Box<dyn IndexStore>,
+        submodule_store_factory: impl FnOnce(&Path) -> Box<dyn SubmoduleStore>,
     ) -> Result<Arc<ReadonlyRepo>, PathError> {
         let repo_path = repo_path.canonicalize().context(repo_path)?;
 
@@ -167,6 +177,14 @@ impl ReadonlyRepo {
         fs::write(&index_type_path, index_store.name()).context(&index_type_path)?;
         let index_store = Arc::from(index_store);
 
+        let submodule_store_path = repo_path.join("submodule_store");
+        fs::create_dir(&submodule_store_path).context(&submodule_store_path)?;
+        let submodule_store = submodule_store_factory(&submodule_store_path);
+        let submodule_store_type_path = submodule_store_path.join("type");
+        fs::write(&submodule_store_type_path, submodule_store.name())
+            .context(&submodule_store_type_path)?;
+        let submodule_store = Arc::from(submodule_store);
+
         let view = View::new(root_view);
         Ok(Arc::new(ReadonlyRepo {
             repo_path,
@@ -179,6 +197,7 @@ impl ReadonlyRepo {
             index: OnceCell::new(),
             change_id_index: OnceCell::new(),
             view,
+            submodule_store,
         }))
     }
 
@@ -190,6 +209,7 @@ impl ReadonlyRepo {
             op_store: self.op_store.clone(),
             op_heads_store: self.op_heads_store.clone(),
             index_store: self.index_store.clone(),
+            submodule_store: self.submodule_store.clone(),
         }
     }
 
@@ -289,6 +309,10 @@ impl Repo for ReadonlyRepo {
         &self.view
     }
 
+    fn submodule_store(&self) -> &Arc<dyn SubmoduleStore> {
+        &self.submodule_store
+    }
+
     fn resolve_change_id_prefix(&self, prefix: &HexPrefix) -> PrefixResolution<Vec<CommitId>> {
         self.change_id_index().resolve_prefix(prefix)
     }
@@ -302,12 +326,14 @@ type BackendFactory = Box<dyn Fn(&Path) -> Box<dyn Backend>>;
 type OpStoreFactory = Box<dyn Fn(&Path) -> Box<dyn OpStore>>;
 type OpHeadsStoreFactory = Box<dyn Fn(&Path) -> Box<dyn OpHeadsStore>>;
 type IndexStoreFactory = Box<dyn Fn(&Path) -> Box<dyn IndexStore>>;
+type SubmoduleStoreFactory = Box<dyn Fn(&Path) -> Box<dyn SubmoduleStore>>;
 
 pub struct StoreFactories {
     backend_factories: HashMap<String, BackendFactory>,
     op_store_factories: HashMap<String, OpStoreFactory>,
     op_heads_store_factories: HashMap<String, OpHeadsStoreFactory>,
     index_store_factories: HashMap<String, IndexStoreFactory>,
+    submodule_store_factories: HashMap<String, SubmoduleStoreFactory>,
 }
 
 impl Default for StoreFactories {
@@ -342,6 +368,12 @@ impl Default for StoreFactories {
             Box::new(|store_path| Box::new(DefaultIndexStore::load(store_path))),
         );
 
+        // SubmoduleStores
+        factories.add_submodule_store(
+            DefaultSubmoduleStore::name(),
+            Box::new(|store_path| Box::new(DefaultSubmoduleStore::load(store_path))),
+        );
+
         factories
     }
 }
@@ -367,6 +399,7 @@ impl StoreFactories {
             op_store_factories: HashMap::new(),
             op_heads_store_factories: HashMap::new(),
             index_store_factories: HashMap::new(),
+            submodule_store_factories: HashMap::new(),
         }
     }
 
@@ -503,6 +536,43 @@ impl StoreFactories {
             })?;
         Ok(index_store_factory(store_path))
     }
+
+    pub fn add_submodule_store(&mut self, name: &str, factory: SubmoduleStoreFactory) {
+        self.submodule_store_factories
+            .insert(name.to_string(), factory);
+    }
+
+    pub fn load_submodule_store(
+        &self,
+        store_path: &Path,
+    ) -> Result<Box<dyn SubmoduleStore>, StoreLoadError> {
+        let submodule_store_type = match fs::read_to_string(store_path.join("type")) {
+            Ok(content) => content,
+            Err(err) if err.kind() == ErrorKind::NotFound => {
+                // For compatibility with repos without repo/submodule_store.
+                // TODO Delete in TBD version
+                let default_type = DefaultSubmoduleStore::name().to_string();
+                fs::create_dir(store_path).unwrap();
+                fs::write(store_path.join("type"), &default_type).unwrap();
+                default_type
+            }
+            Err(err) => {
+                return Err(StoreLoadError::ReadError {
+                    store: "submodule_store",
+                    source: err,
+                });
+            }
+        };
+        let submodule_store_factory = self
+            .submodule_store_factories
+            .get(&submodule_store_type)
+            .ok_or_else(|| StoreLoadError::UnsupportedType {
+                store: "submodule_store",
+                store_type: submodule_store_type.to_string(),
+            })?;
+
+        Ok(submodule_store_factory(store_path))
+    }
 }
 
 #[derive(Clone)]
@@ -513,6 +583,7 @@ pub struct RepoLoader {
     op_store: Arc<dyn OpStore>,
     op_heads_store: Arc<dyn OpHeadsStore>,
     index_store: Arc<dyn IndexStore>,
+    submodule_store: Arc<dyn SubmoduleStore>,
 }
 
 impl RepoLoader {
@@ -527,6 +598,8 @@ impl RepoLoader {
         let op_heads_store =
             Arc::from(store_factories.load_op_heads_store(&repo_path.join("op_heads"))?);
         let index_store = Arc::from(store_factories.load_index_store(&repo_path.join("index"))?);
+        let submodule_store =
+            Arc::from(store_factories.load_submodule_store(&repo_path.join("submodule_store"))?);
         Ok(Self {
             repo_path: repo_path.to_path_buf(),
             repo_settings,
@@ -534,6 +607,7 @@ impl RepoLoader {
             op_store,
             op_heads_store,
             index_store,
+            submodule_store,
         })
     }
 
@@ -589,6 +663,7 @@ impl RepoLoader {
             operation,
             settings: self.repo_settings.clone(),
             index_store: self.index_store.clone(),
+            submodule_store: self.submodule_store.clone(),
             index: OnceCell::with_value(Box::into_pin(index)),
             change_id_index: OnceCell::new(),
             view,
@@ -620,6 +695,7 @@ impl RepoLoader {
             operation,
             settings: self.repo_settings.clone(),
             index_store: self.index_store.clone(),
+            submodule_store: self.submodule_store.clone(),
             index: OnceCell::new(),
             change_id_index: OnceCell::new(),
             view,
@@ -1168,6 +1244,10 @@ impl Repo for MutableRepo {
         self.index.as_index()
     }
 
+    fn submodule_store(&self) -> &Arc<dyn SubmoduleStore> {
+        self.base_repo.submodule_store()
+    }
+
     fn view(&self) -> &View {
         self.view
             .get_or_ensure_clean(|v| self.enforce_view_invariants(v))
diff --git a/lib/src/submodule_store.rs b/lib/src/submodule_store.rs
new file mode 100644
index 000000000..6b0359cbc
--- /dev/null
+++ b/lib/src/submodule_store.rs
@@ -0,0 +1,19 @@
+// Copyright 2023 The Jujutsu Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::fmt::Debug;
+
+pub trait SubmoduleStore: Send + Sync + Debug {
+    fn name(&self) -> &str;
+}
diff --git a/lib/src/workspace.rs b/lib/src/workspace.rs
index fdcca87e7..289612691 100644
--- a/lib/src/workspace.rs
+++ b/lib/src/workspace.rs
@@ -30,6 +30,7 @@ use crate::repo::{
     StoreLoadError,
 };
 use crate::settings::UserSettings;
+use crate::submodule_store::SubmoduleStore;
 use crate::working_copy::WorkingCopy;
 
 #[derive(Error, Debug)]
@@ -163,6 +164,7 @@ impl Workspace {
         op_store_factory: impl FnOnce(&Path) -> Box<dyn OpStore>,
         op_heads_store_factory: impl FnOnce(&Path) -> Box<dyn OpHeadsStore>,
         index_store_factory: impl FnOnce(&Path) -> Box<dyn IndexStore>,
+        submodule_store_factory: impl FnOnce(&Path) -> Box<dyn SubmoduleStore>,
     ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
         let jj_dir = create_jj_dir(workspace_root)?;
         let repo_dir = jj_dir.join("repo");
@@ -174,6 +176,7 @@ impl Workspace {
             op_store_factory,
             op_heads_store_factory,
             index_store_factory,
+            submodule_store_factory,
         )?;
         let (working_copy, repo) = init_working_copy(
             user_settings,
@@ -199,6 +202,7 @@ impl Workspace {
             ReadonlyRepo::default_op_store_factory(),
             ReadonlyRepo::default_op_heads_store_factory(),
             ReadonlyRepo::default_index_store_factory(),
+            ReadonlyRepo::default_submodule_store_factory(),
         )
     }
 
diff --git a/lib/tests/test_git.rs b/lib/tests/test_git.rs
index c40cf7afb..44e3af15d 100644
--- a/lib/tests/test_git.rs
+++ b/lib/tests/test_git.rs
@@ -854,6 +854,7 @@ impl GitRepoData {
             ReadonlyRepo::default_op_store_factory(),
             ReadonlyRepo::default_op_heads_store_factory(),
             ReadonlyRepo::default_index_store_factory(),
+            ReadonlyRepo::default_submodule_store_factory(),
         )
         .unwrap();
         Self {
@@ -1420,6 +1421,7 @@ fn test_init() {
         ReadonlyRepo::default_op_store_factory(),
         ReadonlyRepo::default_op_heads_store_factory(),
         ReadonlyRepo::default_index_store_factory(),
+        ReadonlyRepo::default_submodule_store_factory(),
     )
     .unwrap();
     // The refs were *not* imported -- it's the caller's responsibility to import
@@ -1679,6 +1681,7 @@ fn set_up_push_repos(settings: &UserSettings, temp_dir: &TempDir) -> PushTestSet
         ReadonlyRepo::default_op_store_factory(),
         ReadonlyRepo::default_op_heads_store_factory(),
         ReadonlyRepo::default_index_store_factory(),
+        ReadonlyRepo::default_submodule_store_factory(),
     )
     .unwrap();
     let mut tx = jj_repo.start_transaction(settings, "test");
diff --git a/lib/testutils/src/lib.rs b/lib/testutils/src/lib.rs
index 7b9986989..d5e4b6cfa 100644
--- a/lib/testutils/src/lib.rs
+++ b/lib/testutils/src/lib.rs
@@ -99,6 +99,7 @@ impl TestRepo {
                 ReadonlyRepo::default_op_store_factory(),
                 ReadonlyRepo::default_op_heads_store_factory(),
                 ReadonlyRepo::default_index_store_factory(),
+                ReadonlyRepo::default_submodule_store_factory(),
             )
             .unwrap()
         } else {
@@ -109,6 +110,7 @@ impl TestRepo {
                 ReadonlyRepo::default_op_store_factory(),
                 ReadonlyRepo::default_op_heads_store_factory(),
                 ReadonlyRepo::default_index_store_factory(),
+                ReadonlyRepo::default_submodule_store_factory(),
             )
             .unwrap()
         };