diff --git a/backend/src/api/model/realm/mod.rs b/backend/src/api/model/realm/mod.rs
index 1d3a3307d..2e28a1b2c 100644
--- a/backend/src/api/model/realm/mod.rs
+++ b/backend/src/api/model/realm/mod.rs
@@ -20,7 +20,8 @@ use super::block::{Block, BlockValue, PlaylistBlock, SeriesBlock, VideoBlock};
 mod mutations;
 
 pub(crate) use mutations::{
-    ChildIndex, NewRealm, RemovedRealm, UpdateRealm, UpdatedPermissions, UpdatedRealmName, RealmSpecifier,
+    ChildIndex, NewRealm, RemovedRealm, UpdateRealm, UpdatedPermissions,
+    UpdatedRealmName, RealmSpecifier, RealmLineageComponent, CreateRealmLineageOutcome,
 };
 
 
diff --git a/backend/src/api/model/realm/mutations.rs b/backend/src/api/model/realm/mutations.rs
index 39508106e..a32bf62a7 100644
--- a/backend/src/api/model/realm/mutations.rs
+++ b/backend/src/api/model/realm/mutations.rs
@@ -394,8 +394,19 @@ pub(crate) struct RealmSpecifier {
     pub(crate) path_segment: String,
 }
 
+#[derive(Clone, juniper::GraphQLInputObject)]
+pub(crate) struct RealmLineageComponent {
+    pub(crate) name: String,
+    pub(crate) path_segment: String,
+}
+
 #[derive(juniper::GraphQLObject)]
 #[graphql(Context = Context)]
 pub(crate) struct RemovedRealm {
     parent: Option<Realm>,
 }
+
+#[derive(juniper::GraphQLObject)]
+pub struct CreateRealmLineageOutcome {
+    pub num_created: i32,
+}
diff --git a/backend/src/api/mutation.rs b/backend/src/api/mutation.rs
index 33bf2abac..fd926f934 100644
--- a/backend/src/api/mutation.rs
+++ b/backend/src/api/mutation.rs
@@ -1,7 +1,7 @@
 use juniper::graphql_object;
 
 use crate::{
-    api::model::event::RemovedEvent,
+    api::{err::map_db_err, model::event::RemovedEvent},
     auth::AuthContext,
 };
 use super::{
@@ -21,6 +21,8 @@ use super::{
             UpdatedRealmName,
             UpdateRealm,
             RealmSpecifier,
+            RealmLineageComponent,
+            CreateRealmLineageOutcome,
         },
         block::{
             BlockValue,
@@ -232,6 +234,47 @@ impl Mutation {
         BlockValue::remove(id, context).await
     }
 
+    /// Basically `mkdir -p` for realms: makes sure the given realm lineage
+    /// exists, creating the missing realms. Existing realms are *not* updated.
+    /// Each realm in the given list is the sub-realm of the previous item in
+    /// the list. The first item is sub-realm of the root realm.
+    async fn create_realm_lineage(
+        realms: Vec<RealmLineageComponent>,
+        context: &Context,
+    ) -> ApiResult<CreateRealmLineageOutcome> {
+        if context.auth != AuthContext::TrustedExternal {
+            return Err(not_authorized!("only trusted external applications can use this mutation"));
+        }
+
+        if realms.len() == 0 {
+            return Ok(CreateRealmLineageOutcome { num_created: 0 });
+        }
+
+        if context.config.general.reserved_paths().any(|r| realms[0].path_segment == r) {
+            return Err(invalid_input!(key = "realm.path-is-reserved", "path is reserved and cannot be used"));
+        }
+
+        let mut parent_path = String::new();
+        let mut num_created = 0;
+        for realm in realms {
+            let sql = "\
+                insert into realms (parent, name, path_segment) \
+                values ((select id from realms where full_path = $1), $2, $3) \
+                on conflict do nothing";
+            let res = context.db.execute(sql, &[&parent_path, &realm.name, &realm.path_segment])
+                .await;
+            let affected = map_db_err!(res, {
+                if constraint == "valid_path" => invalid_input!("path invalid"),
+            })?;
+            num_created += affected as i32;
+
+            parent_path.push('/');
+            parent_path.push_str(&realm.path_segment);
+        }
+
+        Ok(CreateRealmLineageOutcome { num_created })
+    }
+
     /// Atomically mount a series into an (empty) realm.
     /// Creates all the necessary realms on the path to the target
     /// and adds a block with the given series at the leaf.
diff --git a/frontend/src/schema.graphql b/frontend/src/schema.graphql
index 34f78c80a..422a33395 100644
--- a/frontend/src/schema.graphql
+++ b/frontend/src/schema.graphql
@@ -229,6 +229,10 @@ input NewVideoBlock {
   showLink: Boolean!
 }
 
+type CreateRealmLineageOutcome {
+  numCreated: Int!
+}
+
 "A `Block`: a UI element that belongs to a realm."
 interface Block {
   id: ID!
@@ -586,6 +590,13 @@ type Mutation {
   updateVideoBlock(id: ID!, set: UpdateVideoBlock!): Block!
   "Remove a block from a realm."
   removeBlock(id: ID!): RemovedBlock!
+  """
+    Basically `mkdir -p` for realms: makes sure the given realm lineage
+    exists, creating the missing realms. Existing realms are *not* updated.
+    Each realm in the given list is the sub-realm of the previous item in
+    the list. The first item is sub-realm of the root realm.
+  """
+  createRealmLineage(realms: [RealmLineageComponent!]!): CreateRealmLineageOutcome!
   """
     Atomically mount a series into an (empty) realm.
     Creates all the necessary realms on the path to the target
@@ -765,6 +776,11 @@ enum ItemType {
   REALM
 }
 
+input RealmLineageComponent {
+  name: String!
+  pathSegment: String!
+}
+
 enum EventSortColumn {
   TITLE
   CREATED