Mother Base is the player-created military base in Metal Gear Solid V: The Phantom Pain.
The offshore facility serves as the headquarters of Diamond Dogs, the private army commanded by Venom Snake. Players expand it by constructing platforms, recruiting personnel, developing weapons, and assigning staff to specialized departments.
Mother Base is both a story location and a major gameplay system. Its development affects research, logistics, medical support, intelligence, and the range of equipment available in the field. Soldiers can also be dismissed, transferred, or managed through the base interface.
The name is inherited from the earlier Metal Gear games, where Big Boss’s forces also maintain a base called Mother Base. Diamond Dogs is the organization operating it in The Phantom Pain, not the facility’s name itself.