Nick Kyrgios lost his U.S. Open match Tuesday night -- and then he lost his mind ... smashing two of his rackets on the court in an epic meltdown at the famous tennis tournament.
Kyrgios battled against Karen Khachanov for nearly four hours with a spot in the tourney's semifinals on the line -- but things started to go awry for the Australian in the fifth set.
Khachanov began taking over, and Kyrgios got frustrated by it -- at one point appearing to yell loudly at people in the stands.
Then, after Khachanov sealed the victory 5-7, 6-4, 5-7, 7-6 (7-3), 4-6, Kyrgios exploded.