He broke a tie with Oscar Robertson, who had 41 triple-doubles in the 1961-62 season.
Westbrook is now leading the league in scoring as well.
But with his 10th assist and the triple-double locked down, Westbrook went to work on the Nuggets' 10-point lead.
Russell Westbrook scored his 42nd triple-double Sunday breaking Oscar Robertson's 55-year record to become the triple-double king of the National Basketball Association.
Westbrook finished the day with 50 points, 16 rebounds and 10 assists.
It was yet another remarkable display of the all-around excellence that a triple-double - the achievement of double-digit totals in three of five key statistical categories - has come to represent. Because of that, their entire story this season has been about Westbrook's record and the team has been built around it. With a 36-foot three-pointer as time expired, the Oklahoma City guard gave the Thunder a 106-105 win to eliminate the Denver Nuggets from playoff contention with two games remaining in the regular season.
Known for his relentless style and frenetic energy, Westbrook was one of six players to start every game this season. Although there are still some doubters about his game and attitude, Westbrook just cemented his name in the history books.
Durant departed to Golden State as a free agent, perhaps a coincidence, the Warriors are the same side who beat Durant and Westbrook previous year in the Western Conference finals.
Instead there was an ovation, and Westbrook raised his hand in a wave when the public address announcer acknowledged the feat.
While congratulating Westbrook on the record, LeBron James said, "There's just certain things you never think you're going to see or never think is going to be broken, and that's one of those records, man".
Oklahoma City Thunder guard Russell Westbrook (0) drives to the basket against Denver Nuggets guard Gary Harris (14) during the second half at Pepsi Center in Denver on April 9, 2017.
"Y'all are probably going to get exhausted of me saying the same thing, but I promise you I've been blessed with so many things".