Clarke followed in the footsteps of the likes of Lennox Lewis, Joe Joyce, David Price and Audley Harrison by scooping the men's super-heavyweight title at the Commonwealths, edging past his Indian opponent to win gold.
A close contest saw Kumar edge the first round on the scorecards of three of the five judges, but Clarke reacted to that with an improved performance in the second round, which four judges deemed him to have won.
All five were agreed that he won the final round, meanwhile, earning the 26-year-old a unanimous points decision despite only one point separating the fighters on four of the judges' final scorecards.
"I'm so happy right now. That was close, very close, and what a good fighter Kumar was. He made it a bit rough and tumble in there," he told reporters after the fight.
"I felt a bit flat myself but landed the clean shots and managed to catch him as he was coming in, those little shots that aren't so obvious. I got the win and that's all that matters.
"First of all, I've got to keep improving. I want to be doing a better job but I want to go all the way. The Olympics is my dream but I'll have to work very hard and improve to get there."
Clarke's win capped off a successful final day of boxing for England as they picked up five gold medals from the six finals they contested.