Luke Walton melted down on the court during a timeout Thursday night -- karate-chopping a clipboard straight to the ground -- and the whole temper tantrum was caught on video.
The Sacramento Kings coach was furious with his squad in the 4th quarter of their game with the NY Knicks ... and when an assistant tried to hand him a whiteboard, Walton lost it.
The dude reared back with his fist and fired straight down into the board ... causing it to break into pieces.
Walton then appeared to yell at his team ... before the Kings went on to lose 140-121.
Afterward, Luke said the temper tantrum was simply a release of frustration ... with the coach admitting he's straight-up tired of the Kings' recent poor play.
"Look, I'm frustrated. We all should be frustrated," Walton said ... "I was frustrated tonight and I believe in our team and I know when our group is playing well, we are much better than what we showed tonight."
Walton and the Kings have been in a serious slump ... losing 9 straight games and dropping their record to just 12-20 in the process.
Clearly, Walton is hoping for a turnaround ... could a clipboard freakout be the catalyst his team needs?
Kings play next against the Pistons on Friday night ... stay tuned.