U.S. Olympian Joshua Mance -- There's One Porn Star ... I Really Wanna Date!

He won a silver medal at the 2012 Olympics ... but Team USA sprinter Josh Mance says the real prize would be a date with his favorite porn actress -- the star of "Weapons of Ass Destruction 7."

The 22-year-old speedster was at LAX when he told us he's got a serious crush on Skin Diamond -- who's appeared in more than 139 films and won AVN awards for Best Oral and Best DP in 2014.

"She's killing the game right now," Mance tells TMZ Sports ... "She has this innocence to her."

No word if Miss Diamond is interested or not -- but we'll find out. In the meantime, check out the pics ...