10:01 AM PT -- Sources close to Amelia tell TMZ, SHE is the one who broke up with him, not vice versa. We're told Amelia had it once Scott sent that DM to Younes about Kourtney. One source said, "The breakup was coming, but the Younes DM was the final straw."
Scott Disick is a single man again ... he and his 20-year-old girlfriend, Amelia Hamlin, are no more.
Sources close to Scott tell TMZ ... things had been falling apart between Scott and Amelia for weeks and over the holiday weekend, they officially ended things.
Our sources say Scott is the one who called it quits ... we're told it wasn't anything personal, he just didn't see a future with Amelia long-term, and didn't want to keep wasting his time or hers.