Timothée Chalamet is trading the Met Gala for The Mecca of Basketball.

The A-Lister is sitting courtside at an important playoff game for his favorite NBA team instead of accompanying his "partner of three years" Kylie Jenner to the biggest night in fashion.

Timmy is a huge New York Knicks fan ... and he's front and center at halfcourt watching the home team play the visiting Philadelphia 76ers in the first game of their playoff series.

Meanwhile, Kylie is across town celebrating the first Monday in May ... and she's nipping out.

Timothée choosing the Knicks over Kylie shouldn't be a huge surprise if you've been paying attention ... he skipped the Met Gala last year to watch the Knicks on TV.

This year, the Knicks are playing at home ... so it seems Timothée had an even easier decision.

Courtside at Madison Square Garden ... that's hard to beat. Better luck next year, Met Gala!!!