What is the name of the first black superhero in mainstream American comics?

The first Black superhero in mainstream American comics is Black Panther. Marvel introduced him in Fantastic Four #52, published in July 1966, as T’Challa, king of the fictional African nation Wakanda.

Created by Stan Lee and Jack Kirby, Black Panther was notable as a powerful, intelligent, non-caricatured Black hero who was also a monarch and statesman. His technologically advanced nation is built around vibranium, the fictional metal that gives Wakanda much of its wealth and defensive power.

The wording matters: earlier Black characters appeared in comics, including Lothar from Mandrake the Magician and characters in All-Negro Comics #1, but Black Panther is conventionally credited as the first Black superhero in mainstream American comics. Falcon, John Stewart, and Luke Cage came later; Luke Cage was the first Black superhero to headline his own mainstream comic-book series.