Can you run a database on an Android phone?

Short answer

Yes. One engine runs on the device itself — an embedded PostgreSQL 18.2 server, on 64-bit ARM phones — so you create tables, run SQL, browse data and design ER diagrams with no desktop and no cloud host. Eleven more (MySQL/MariaDB, MongoDB, Redis, Supabase, Neon, PlanetScale, Turso, Cloudflare D1, MongoDB Atlas, Upstash, Firestore) connect to your own server or a cloud service and need a network, on Android 9 or newer, with backups and data masking built in.