Bosses are strong enemies found at the end of every floor in The Gungeon. Defeating a boss allows the player to advance to the next floor.
Upon being killed, bosses drop a weapon or item of random quality, several Hegemony Credits, and one to three pickups such as hearts, ammo, or keys. Bosses will always drop a gun if the player has not yet picked up a gun on the current floor. If a boss from one of the five main floors is defeated without taking damage, they will drop a Master Round as well.
- When the player enters the past, they will lose their items and guns, but will keep blanks and armor.
- Bosses have a damage per second cap that varies per floor:
- The damage per second cap is ignored by Makeshift Cannon and Yari Launcher.
- In Boss Rush, bosses have no damage per second cap.
- The damage per second cap is ignored if a weapon deals 1000 or more damage.