Logic's wasting little time getting back in the saddle ... or in his case, in a private jet with a new chick.

Our Logic sources say the rapper boarded a jet bound for Vegas to do a show last week, and had a 19-year-old hot blonde with him, who we're told is named Brittney. She and Logic met earlier this year.

Sources say Brittney works at a juice shop in Calabasas that he frequents. It's unclear when they started dating.

TMZ broke the story ... Logic pulled the plug on his marriage last month from Jessica Andrea, and divorce is looming. As we first reported, Logic and Jessica have a prenup, but we're told there's some wrangling about the terms.