Notre Dame WR Justin Brent -- DATING BOOTY MODEL ... After Fling with Porn Star

Notre Dame WR Justin Brent -- the guy who dated porn star Lisa Ann -- has moved on to thicker pastures ... and is now dating one of the most famous booty models in the ass game ... TMZ Sports has learned.

Of course, Brent's brief relationship with the 42-year-old porn Hall of Famer made national headlines earlier this year ... since the 19-year-old goes to a Catholic university which frowns upon pre-marital sex.

But now it seems Lisa Ann is out ... replaced by Elke the Stallion -- whose 36DD-30-50 measurements have made her an Internet superstar ... and recently scored her a major part in Major Lazer's "Bubble Butt" video.

We spoke with Elke who says she first met Brent through social media ... but the cyber-flirting escalated to the point where she decided to attend the USC-ND game in L.A. last month to meet Brent in person.

Elke says the two hit it off ... "He's a mad cool dude. Very respectful. Not an Idiot like the rest of them."

So how serious are they? Elke claims it's too early to tell ... but says "you never know" where things could end up.

Justin Brent -- the legend continues ...