Mark Sanchez & Eva Longoria -- Fancy French Night

Yeah, Mark Sanchez and Eva Longoria are definitely doing it.

The freshly-minted couple left the Ritz-Carlton in NYC for a late night dinner at the uber-fancy French restaurant Daniel.

The New York Jets QB is 25 -- she's 37.

Having just divorced another professional athlete -- NBA star Tony Parker -- Eva's clearly got a thing. As for Sanchez, he was previously banging 20-year-old Kate Upton.

So we gotta ask ...