diff --git a/src/models/database/__init__.py b/src/models/database/__init__.py
index a01a86e5c..9a4d012fb 100644
--- a/src/models/database/__init__.py
+++ b/src/models/database/__init__.py
@@ -1 +1,5 @@
 """Database models package."""
+
+from models.database.prompts import Prompt, PromptVersion
+
+__all__ = ["Prompt", "PromptVersion"]
diff --git a/src/models/database/prompts.py b/src/models/database/prompts.py
new file mode 100644
index 000000000..cf701acda
--- /dev/null
+++ b/src/models/database/prompts.py
@@ -0,0 +1,58 @@
+"""Persistence models for the versioned prompt catalog."""
+
+from datetime import datetime
+
+from sqlalchemy import JSON, DateTime, ForeignKey, String, Text, func
+from sqlalchemy.orm import Mapped, mapped_column, validates
+
+from models.database.base import Base
+from prompts.exceptions import PromptValidationError
+
+
+class Prompt(Base):  # pylint: disable=too-few-public-methods
+    """Prompt identity with a pointer to the default version."""
+
+    __tablename__ = "prompt"
+
+    id: Mapped[str] = mapped_column(primary_key=True)
+
+    name: Mapped[str] = mapped_column(String(255))
+
+    default_version: Mapped[int] = mapped_column()
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now()
+    )
+
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
+    )
+
+
+class PromptVersion(Base):  # pylint: disable=too-few-public-methods
+    """Immutable version row containing the template text and declared variables."""
+
+    __tablename__ = "prompt_version"
+
+    # Foreign key is not turned on by default for sqlite, but a PromptVersion will always
+    # be created after a Prompt is created in the database operation logic. Therefore,
+    # a PromptVersion with a nonexistent prompt.id will never be created.
+    prompt_id: Mapped[str] = mapped_column(ForeignKey("prompt.id"), primary_key=True)
+
+    version: Mapped[int] = mapped_column(primary_key=True)
+
+    template: Mapped[str] = mapped_column(Text())
+
+    variables: Mapped[list[str]] = mapped_column(JSON, default=list)
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now()
+    )
+
+    @validates("variables")
+    def validate_unique_variables(self, _key: str, value: list[str]) -> list[str]:
+        """Ensure no duplicate variable names."""
+        if len(value) != len(set(value)):
+            raise PromptValidationError("The variables contain duplicate names")
+
+        return value
diff --git a/src/prompts/__init__.py b/src/prompts/__init__.py
new file mode 100644
index 000000000..14fcd39dd
--- /dev/null
+++ b/src/prompts/__init__.py
@@ -0,0 +1 @@
+"""Prompts module for the versioned prompt catalog."""
diff --git a/src/prompts/exceptions.py b/src/prompts/exceptions.py
new file mode 100644
index 000000000..8b23ce113
--- /dev/null
+++ b/src/prompts/exceptions.py
@@ -0,0 +1,9 @@
+"""Domain exceptions for the prompts module."""
+
+
+class PromptError(Exception):
+    """Base class for prompt domain errors."""
+
+
+class PromptValidationError(PromptError):
+    """Invalid prompt field values."""
diff --git a/tests/unit/models/database/test_prompts.py b/tests/unit/models/database/test_prompts.py
new file mode 100644
index 000000000..6e998d20a
--- /dev/null
+++ b/tests/unit/models/database/test_prompts.py
@@ -0,0 +1,311 @@
+"""Unit tests for Prompt and PromptVersion database models."""
+
+from collections.abc import Generator
+
+import pytest
+from sqlalchemy import String, create_engine, inspect, text
+from sqlalchemy.engine import Engine
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import Session, sessionmaker
+from sqlalchemy.pool import StaticPool
+
+from models.database.base import Base
+from models.database.prompts import Prompt, PromptVersion
+from prompts.exceptions import PromptValidationError
+
+
+@pytest.fixture(name="sqlite_engine")
+def sqlite_engine_fixture() -> Generator[Engine, None, None]:
+    """Provide an in-memory SQLite engine with all tables created.
+
+    Yields:
+        Engine: A SQLAlchemy Engine bound to an in-memory SQLite database with
+        tables created from Base.metadata.
+
+    """
+    engine = create_engine(
+        "sqlite:///:memory:",
+        echo=False,
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    Base.metadata.create_all(engine)
+    yield engine
+    engine.dispose()
+
+
+@pytest.fixture(name="db_session")
+def db_session_fixture(sqlite_engine: Engine) -> Generator[Session, None, None]:
+    """Provide a database session for tests.
+
+    Parameters:
+        sqlite_engine: In-memory SQLite engine fixture.
+
+    Yields:
+        Session: A SQLAlchemy Session bound to the test engine.
+
+    """
+    session_factory = sessionmaker(
+        autocommit=False, autoflush=False, bind=sqlite_engine
+    )
+    session = session_factory()
+    try:
+        yield session
+    finally:
+        session.close()
+
+
+@pytest.fixture(name="sample_prompt")
+def sample_prompt_fixture(db_session: Session) -> Prompt:
+    """Insert and return a sample Prompt row.
+
+    Parameters:
+        db_session: Active database session.
+
+    Returns:
+        Prompt: The persisted prompt instance.
+
+    """
+    prompt = Prompt(id="pmpt_001", name="greeting", default_version=1)
+    db_session.add(prompt)
+    db_session.commit()
+    return prompt
+
+
+class TestPromptModelDefinition:
+    """Test cases for Prompt model schema definition."""
+
+    def test_tablename(self) -> None:
+        """Test Prompt uses the expected table name."""
+        assert Prompt.__tablename__ == "prompt"
+
+    def test_expected_columns_exist(self) -> None:
+        """Test Prompt defines all expected columns."""
+        column_names = {col.name for col in Prompt.__table__.columns}
+        expected = {"id", "name", "default_version", "created_at", "updated_at"}
+        assert column_names == expected
+
+    def test_name_column_max_length(self) -> None:
+        """Test name column has max length 255."""
+        name_column = Prompt.__table__.c.name
+        assert isinstance(name_column.type, String)
+        assert name_column.type.length == 255
+
+    def test_id_is_primary_key(self) -> None:
+        """Test id column is the primary key."""
+        assert Prompt.__table__.c.id.primary_key
+
+
+class TestPromptVersionModelDefinition:
+    """Test cases for PromptVersion model schema definition."""
+
+    def test_tablename(self) -> None:
+        """Test PromptVersion uses the expected table name."""
+        assert PromptVersion.__tablename__ == "prompt_version"
+
+    def test_expected_columns_exist(self) -> None:
+        """Test PromptVersion defines all expected columns."""
+        column_names = {col.name for col in PromptVersion.__table__.columns}
+        expected = {"prompt_id", "version", "template", "variables", "created_at"}
+        assert column_names == expected
+
+    def test_composite_primary_key(self) -> None:
+        """Test primary key is (prompt_id, version)."""
+        pk_columns = {col.name for col in PromptVersion.__table__.primary_key.columns}
+        assert pk_columns == {"prompt_id", "version"}
+
+    def test_prompt_id_has_foreign_key(self) -> None:
+        """Test prompt_id references prompt.id."""
+        fk_targets = {
+            fk.target_fullname
+            for fk in PromptVersion.__table__.c.prompt_id.foreign_keys
+        }
+        assert "prompt.id" in fk_targets
+
+
+class TestPromptDatabaseOperations:
+    """Test cases for Prompt database operations."""
+
+    def test_tables_created_by_metadata(self, sqlite_engine: Engine) -> None:
+        """Test prompt and prompt_version tables are created via Base.metadata."""
+        inspector = inspect(sqlite_engine)
+        table_names = inspector.get_table_names()
+        assert "prompt" in table_names
+        assert "prompt_version" in table_names
+
+    def test_insert_and_read_prompt(self, db_session: Session) -> None:
+        """Test inserting and reading back a Prompt row."""
+        prompt = Prompt(id="pmpt_001", name="greeting", default_version=1)
+        db_session.add(prompt)
+        db_session.commit()
+
+        result = db_session.get(Prompt, "pmpt_001")
+        assert result is not None
+        assert result.id == "pmpt_001"
+        assert result.name == "greeting"
+        assert result.default_version == 1
+        assert result.created_at is not None
+        assert result.updated_at is not None
+
+    def test_duplicate_prompt_id_raises_integrity_error(
+        self, db_session: Session
+    ) -> None:
+        """Test inserting duplicate prompt id raises IntegrityError."""
+        db_session.add(Prompt(id="pmpt_001", name="first", default_version=1))
+        db_session.commit()
+
+        db_session.add(Prompt(id="pmpt_001", name="second", default_version=1))
+        with pytest.raises(IntegrityError):
+            db_session.commit()
+
+
+class TestPromptVersionDatabaseOperations:
+    """Test cases for PromptVersion database operations."""
+
+    def test_insert_and_read_version(
+        self, db_session: Session, sample_prompt: Prompt
+    ) -> None:
+        """Test inserting and reading back a PromptVersion row."""
+        version = PromptVersion(
+            prompt_id=sample_prompt.id,
+            version=1,
+            template="Hello {{name}}",
+            variables=["name"],
+        )
+        db_session.add(version)
+        db_session.commit()
+
+        result = db_session.get(PromptVersion, (sample_prompt.id, 1))
+        assert result is not None
+        assert result.prompt_id == sample_prompt.id
+        assert result.version == 1
+        assert result.template == "Hello {{name}}"
+        assert result.variables == ["name"]
+        assert result.created_at is not None
+
+    def test_multiple_versions_for_same_prompt(
+        self, db_session: Session, sample_prompt: Prompt
+    ) -> None:
+        """Test that a prompt can have multiple versions."""
+        v1 = PromptVersion(
+            prompt_id=sample_prompt.id,
+            version=1,
+            template="Hello {{name}}",
+            variables=["name"],
+        )
+        v2 = PromptVersion(
+            prompt_id=sample_prompt.id,
+            version=2,
+            template="Hi {{name}}, welcome to {{place}}",
+            variables=["name", "place"],
+        )
+        db_session.add_all([v1, v2])
+        db_session.commit()
+
+        results = (
+            db_session.query(PromptVersion)
+            .filter_by(prompt_id=sample_prompt.id)
+            .order_by(PromptVersion.version)
+            .all()
+        )
+        assert len(results) == 2
+        assert results[0].version == 1
+        assert results[1].version == 2
+
+    def test_duplicate_prompt_id_and_version_raises_integrity_error(
+        self, db_session: Session, sample_prompt: Prompt
+    ) -> None:
+        """Test inserting duplicate (prompt_id, version) raises IntegrityError."""
+        db_session.add(
+            PromptVersion(
+                prompt_id=sample_prompt.id,
+                version=1,
+                template="first",
+                variables=[],
+            )
+        )
+        db_session.commit()
+
+        db_session.add(
+            PromptVersion(
+                prompt_id=sample_prompt.id,
+                version=1,
+                template="second",
+                variables=[],
+            )
+        )
+        with pytest.raises(IntegrityError):
+            db_session.commit()
+
+    def test_foreign_key_enforced(self, db_session: Session) -> None:
+        """Test inserting a version for a non-existent prompt raises IntegrityError."""
+        db_session.execute(text("PRAGMA foreign_keys = ON"))
+        version = PromptVersion(
+            prompt_id="nonexistent",
+            version=1,
+            template="Hello",
+            variables=[],
+        )
+        db_session.add(version)
+        with pytest.raises(IntegrityError):
+            db_session.commit()
+
+    def test_empty_variables_defaults_to_list(
+        self, db_session: Session, sample_prompt: Prompt
+    ) -> None:
+        """Test that variables defaults to an empty list."""
+        version = PromptVersion(
+            prompt_id=sample_prompt.id,
+            version=1,
+            template="No placeholders here",
+        )
+        db_session.add(version)
+        db_session.commit()
+
+        result = db_session.get(PromptVersion, (sample_prompt.id, 1))
+        assert result is not None
+        assert result.variables == []
+
+
+class TestPromptVersionVariableValidation:
+    """Test cases for PromptVersion variable uniqueness validation."""
+
+    def test_unique_variables_accepted(self) -> None:
+        """Test that a list of unique variable names is accepted."""
+        version = PromptVersion(
+            prompt_id="pmpt_001",
+            version=1,
+            template="{{a}} {{b}}",
+            variables=["a", "b"],
+        )
+        assert version.variables == ["a", "b"]
+
+    def test_duplicate_variables_raises_validation_error(self) -> None:
+        """Test that duplicate variable names raise PromptValidationError."""
+        with pytest.raises(PromptValidationError, match="duplicate names"):
+            PromptVersion(
+                prompt_id="pmpt_001",
+                version=1,
+                template="{{a}} {{a}}",
+                variables=["a", "a"],
+            )
+
+    def test_empty_variables_accepted(self) -> None:
+        """Test that an empty variable list is accepted."""
+        version = PromptVersion(
+            prompt_id="pmpt_001",
+            version=1,
+            template="No variables",
+            variables=[],
+        )
+        assert version.variables == []
+
+    def test_single_variable_accepted(self) -> None:
+        """Test that a single variable is accepted."""
+        version = PromptVersion(
+            prompt_id="pmpt_001",
+            version=1,
+            template="{{name}}",
+            variables=["name"],
+        )
+        assert version.variables == ["name"]