Did Lance Bass Steal Marc Jacobs' Boyfriend?

Marc Jacobs recently called it quits with his long term boyfriend-turned-fiance Lorenzo Martone, but after only two months, Martone is moving on -- with 'N Syncer Lance Bass!

The two apparently met while Martone was still with Jacobs -- but according to the NY Daily News they didn't *officially* hook up until Marc and Lorenzo were dunzo.

The two were first spotted gettin' flirty at The Soho house in NYC on June 6th, but since then, they've been out on several dates in the city says a source!

But before you think this may lead to something serious, not so, says a Lance pal.

"Lorenzo is trying to make it more than it is," and Lance is just "not that interested." Plus, Lance, who's 31, prefers to get with guys who are "younger and prettier" than the 31-year-old Martone.

Whoops!