diff --git a/crates/db/src/lib.rs b/crates/db/src/lib.rs
index 7e1475a..403e041 100644
--- a/crates/db/src/lib.rs
+++ b/crates/db/src/lib.rs
@@ -4,6 +4,7 @@ pub mod audit;
 pub mod authority;
 pub mod catalog;
 pub mod fields;
+pub mod seed;
 pub mod vocab;
 
 use sqlx::postgres::{PgPool, PgPoolOptions};
diff --git a/crates/db/src/seed.rs b/crates/db/src/seed.rs
new file mode 100644
index 0000000..dfb7c0b
--- /dev/null
+++ b/crates/db/src/seed.rs
@@ -0,0 +1,160 @@
+//! Seed data: a representative subset of the Spectrum Cataloguing field set.
+//!
+//! Idempotent — each vocabulary and field definition is created only if a row with
+//! that key does not already exist. Vocabularies are seeded empty; their terms are
+//! populated by the organization or a later import. The inventory-minimum fields
+//! (object number, name, location, …) live in the typed object core, not here.
+
+use domain::{AuthorityKind, FieldType, LocalizedLabel, NewFieldDefinition, VocabularyId};
+
+use crate::{fields, vocab};
+
+/// Seed the Spectrum cataloguing vocabularies and field definitions on `conn`.
+/// Pass a transaction connection (`&mut *tx`) so the whole seed is atomic.
+pub async fn seed_spectrum_cataloguing(conn: &mut sqlx::PgConnection) -> Result<(), sqlx::Error> {
+    let material = ensure_vocabulary(conn, "material").await?;
+    let object_name = ensure_vocabulary(conn, "object_name").await?;
+    let technique = ensure_vocabulary(conn, "technique").await?;
+
+    let definitions = [
+        def(
+            "object_type",
+            FieldType::Term {
+                vocabulary_id: object_name,
+            },
+            "identification",
+            &[("sv", "Sakord"), ("en", "Object type")],
+        ),
+        def(
+            "title",
+            FieldType::LocalizedText,
+            "identification",
+            &[("sv", "Titel"), ("en", "Title")],
+        ),
+        def(
+            "comments",
+            FieldType::Text,
+            "identification",
+            &[("sv", "Kommentarer"), ("en", "Comments")],
+        ),
+        def(
+            "material",
+            FieldType::Term {
+                vocabulary_id: material,
+            },
+            "description",
+            &[("sv", "Material"), ("en", "Material")],
+        ),
+        def(
+            "technique",
+            FieldType::Term {
+                vocabulary_id: technique,
+            },
+            "description",
+            &[("sv", "Teknik"), ("en", "Technique")],
+        ),
+        def(
+            "physical_description",
+            FieldType::Text,
+            "description",
+            &[("sv", "Fysisk beskrivning"), ("en", "Physical description")],
+        ),
+        def(
+            "dimensions",
+            FieldType::Text,
+            "description",
+            &[("sv", "Mått"), ("en", "Dimensions")],
+        ),
+        def(
+            "inscription",
+            FieldType::Text,
+            "description",
+            &[("sv", "Inskription"), ("en", "Inscription")],
+        ),
+        def(
+            "content_description",
+            FieldType::Text,
+            "content",
+            &[
+                ("sv", "Innehållsbeskrivning"),
+                ("en", "Content description"),
+            ],
+        ),
+        def(
+            "production_date",
+            FieldType::Date,
+            "production",
+            &[("sv", "Tillverkningsdatum"), ("en", "Production date")],
+        ),
+        def(
+            "production_place",
+            FieldType::Authority {
+                kind: Some(AuthorityKind::Place),
+            },
+            "production",
+            &[("sv", "Tillverkningsplats"), ("en", "Production place")],
+        ),
+        def(
+            "production_person",
+            FieldType::Authority {
+                kind: Some(AuthorityKind::Person),
+            },
+            "production",
+            &[("sv", "Tillverkare"), ("en", "Producer")],
+        ),
+    ];
+
+    for definition in &definitions {
+        ensure_field_definition(conn, definition).await?;
+    }
+
+    Ok(())
+}
+
+/// Get-or-create a vocabulary by key, returning its id.
+async fn ensure_vocabulary(
+    conn: &mut sqlx::PgConnection,
+    key: &str,
+) -> Result<VocabularyId, sqlx::Error> {
+    if let Some(existing) = vocab::vocabulary_by_key(&mut *conn, key).await? {
+        Ok(existing.id)
+    } else {
+        Ok(vocab::create_vocabulary(&mut *conn, key).await?.id)
+    }
+}
+
+/// Create a field definition only if its key is not already present.
+async fn ensure_field_definition(
+    conn: &mut sqlx::PgConnection,
+    definition: &NewFieldDefinition,
+) -> Result<(), sqlx::Error> {
+    if fields::field_definition_by_key(&mut *conn, &definition.key)
+        .await?
+        .is_none()
+    {
+        fields::create_field_definition(&mut *conn, definition).await?;
+    }
+
+    Ok(())
+}
+
+fn def(
+    key: &str,
+    field_type: FieldType,
+    group: &str,
+    label_pairs: &[(&str, &str)],
+) -> NewFieldDefinition {
+    NewFieldDefinition {
+        key: key.to_owned(),
+        field_type,
+        required: false,
+        group_key: Some(group.to_owned()),
+        labels: label_pairs
+            .iter()
+            .map(|(lang, label)| LocalizedLabel {
+                lang: (*lang).to_owned(),
+                label: (*label).to_owned(),
+            })
+            .collect(),
+    }
+}
diff --git a/crates/db/tests/seed.rs b/crates/db/tests/seed.rs
new file mode 100644
index 0000000..821927d
--- /dev/null
+++ b/crates/db/tests/seed.rs
@@ -0,0 +1,92 @@
+use db::{Db, fields, seed, vocab};
+use domain::{AuthorityKind, FieldType};
+use sqlx::PgPool;
+
+#[sqlx::test]
+async fn seed_creates_vocabularies_and_field_definitions(pool: PgPool) {
+    let db = Db::from_pool(pool);
+
+    let mut tx = db.pool().begin().await.unwrap();
+    seed::seed_spectrum_cataloguing(&mut tx).await.unwrap();
+    tx.commit().await.unwrap();
+
+    for key in ["material", "object_name", "technique"] {
+        assert!(
+            vocab::vocabulary_by_key(db.pool(), key)
+                .await
+                .unwrap()
+                .is_some(),
+            "vocabulary {key} should be seeded"
+        );
+    }
+
+    let material_vocab = vocab::vocabulary_by_key(db.pool(), "material")
+        .await
+        .unwrap()
+        .unwrap();
+    let material_field = fields::field_definition_by_key(db.pool(), "material")
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(
+        material_field.field_type,
+        FieldType::Term {
+            vocabulary_id: material_vocab.id
+        }
+    );
+
+    let place = fields::field_definition_by_key(db.pool(), "production_place")
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(
+        place.field_type,
+        FieldType::Authority {
+            kind: Some(AuthorityKind::Place)
+        }
+    );
+
+    let title = fields::field_definition_by_key(db.pool(), "title")
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(title.field_type, FieldType::LocalizedText);
+    let date = fields::field_definition_by_key(db.pool(), "production_date")
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(date.field_type, FieldType::Date);
+
+    assert_eq!(
+        fields::list_field_definitions(db.pool())
+            .await
+            .unwrap()
+            .len(),
+        12
+    );
+}
+
+#[sqlx::test]
+async fn seed_is_idempotent(pool: PgPool) {
+    let db = Db::from_pool(pool);
+
+    for _ in 0..2 {
+        let mut tx = db.pool().begin().await.unwrap();
+        seed::seed_spectrum_cataloguing(&mut tx).await.unwrap();
+        tx.commit().await.unwrap();
+    }
+
+    assert_eq!(
+        fields::list_field_definitions(db.pool())
+            .await
+            .unwrap()
+            .len(),
+        12
+    );
+    assert!(
+        vocab::vocabulary_by_key(db.pool(), "material")
+            .await
+            .unwrap()
+            .is_some()
+    );
+}