diff --git a/backend/app/database.py b/backend/app/database.py
new file mode 100644
index 0000000..597d553
--- /dev/null
+++ b/backend/app/database.py
@@ -0,0 +1,42 @@
+"""Database engine, session, and base model."""
+from sqlalchemy import create_engine, event
+from sqlalchemy.orm import sessionmaker, DeclarativeBase
+from app.config import settings
+
+
+# Engine
+if settings.DATABASE_URL.startswith("sqlite"):
+    engine = create_engine(
+        settings.DATABASE_URL,
+        connect_args={"check_same_thread": False},
+        echo=False,
+    )
+    # Enable foreign keys for SQLite
+    @event.listens_for(engine, "connect")
+    def _fk_pragma_on_connect(dbapi_con, con_record):
+        cursor = dbapi_con.cursor()
+        cursor.execute("PRAGMA foreign_keys=ON")
+        cursor.close()
+else:
+    engine = create_engine(settings.DATABASE_URL, echo=False, pool_pre_ping=True)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+class Base(DeclarativeBase):
+    """Declarative base for all models."""
+    pass
+
+
+def get_db():
+    """FastAPI dependency: yields a database session."""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+def init_db():
+    """Create all tables (used for dev / first run)."""
+    Base.metadata.create_all(bind=engine)