Timothée Chalamet had a pretty good reason to let Kylie Jenner fly solo at the Met Gala … his NBA team was playing an important playoff game, and he had to watch!!!

The actor, who is a big Knicks fan, was nowhere to be found at Monday’s Met Gala in New York City … instead, he was tuning in to watch the Knicks play the Boston Celtics in Game 1 of their series.

Timothée may have made the right call here … the Knicks won in thrilling fashion, storming back from a 20-point deficit to shock the defending-champion Celtics in overtime, 108-105, to steal home court advantage in the best-of-7 series.

Timothée and Kylie were making out courtside at a Lakers playoff game last week in Los Angeles … the Lakers lost that game, so maybe it’s a good thing the Knicks were playing in Boston and Timothée was cheering from the couch.

As for Kylie, she wouldn’t miss the Met Gala for an NBA game … and she looked stunning as usual.

The Knicks host the Celtics in Games 3 and 4 on Saturday and Monday at Madison Square Garden … and it will be interesting to see if Timothée and Kylie are in the house.