Kim Kardashian With Saint at Lionel Messi's First MLS Game, Plus LeBron and Tristan

Kim Kardashian is taking her soccer mom game to the next level ... bringing son Saint with her to Lionel Messi's first game with his new Major League Soccer club.

Kim and Saint are among the celebs in the house for Messi's debut with Inter Miami ... she says they're there to support Saint's passion for soccer, and root on his favorite player, Messi.

Remember ... Kim and Saint have been to soccer games around the world this year, we saw them back in March at a match in Paris.

Kim and Saint are seeing some familiar faces at the game ... because Tristan Thompson is also in the house.

Serena Williams made sure to catch Messi's first game ... and LeBron James did too, even sharing a moment with the soccer star before the game.

Messi's new Inter Miami team is playing Mexican club Cruz Azul at DRV PNK Stadium in Fort Lauderdale ... and he's coming off the bench and expected to play the last 30 minutes.