John Stewart is the first Green Lantern recruited by the Guardians in the DC series Lanterns.
The series presents Stewart as an anomaly in Green Lantern Corps history. Instead of being chosen by a power ring in the customary way, he is recruited directly by the Guardians of the Universe. This unusual origin is one of the show’s distinctive changes to the character’s backstory.
Stewart is also a new recruit whom Hal Jordan trains to replace himself. The contrast between Jordan’s experience and Stewart’s unusual recruitment helps define their partnership. Their relationship is central to the show’s buddy-cop structure as they investigate a murder in Rushville, Nebraska.
The series version of Stewart has a dual identity as a former Marine and an artistic architect. That combination was important to Chris Mundy, who wanted Aaron Pierre to convey both sides of the character. The question refers specifically to Lanterns’ continuity, not necessarily to every version of John Stewart in DC Comics.