The ganzá (Portuguese pronunciation: [ɡɐ̃ˈza]) is a Brazilian rattle used as a percussion instrument, especially in samba music.

The ganzá is cylinder-shaped and can be made as a hand-woven basket or a metal canister filled with beads, metal balls, pebbles, or similar items. Metal ganzás create a very loud sound. They are used to play a rhythm that supports the rest of the music.

The ganzá is often used in Brazilian samba music to add a background rhythm.

It is classified as an indirectly struck idiophone.