Timothée Chalamet fans waited for hours in line to get some "Marty Supreme" merch at a Los Angeles pop up shop ... and the crowd grew so huge, cops were called.

Check out these videos from the 'Marty' pop-up shop in L.A. ... this is on a Monday afternoon, and there's a line down the block with tons of people trying to squeeze inside to get their hands on merch. Play video content

The woman managing the space came out and had to tell folks if they didn't have a ticket, they needed to get out of line, and there were tons of security and fencing in place ... but police still ended up being called.

Video shows several officers at the pop-up deciding whether to declare this an unlawful assembly.

LAPD tells TMZ … officers responded to a large group at 1:53 PM, and when officers arrived,

See Full Page