What is the name of the final boss in the original Metroid?

The final boss in the original Metroid is Mother Brain. Samus reaches her in Tourian, the Space Pirates’ heavily guarded base on Zebes, after defeating the other major bosses, Kraid and Ridley.

Mother Brain is a biomechanical supercomputer originally created by the Chozo. In the original game, she appears inside a glass container and controls the defenses and operations of the Space Pirates. Samus must first destroy the container before she can damage the exposed brain.

A common mix-up is Ridley, who is one of Metroid’s most famous villains and a major boss, but he is not the final encounter. Mother Brain returns in Super Metroid with a much larger body and a more elaborate battle. The original Metroid was released in 1986, while its enhanced remake, Metroid: Zero Mission, revisits the same conflict with expanded story and gameplay.