Oscar De La Hoya loves his girlfriend sooooo much ... he rented out an entire bar and threw a kick-ass party for her birthday ... and TMZ Sports has the vid!!
Sources tell us the Golden Boy booked the White Horse in Pasadena last weekend for Anna Valencia's 30th ... decking the place out in a casino theme, complete with blackjack tables and chips featuring her face!!
We're told the boxing champ footed the entire bill for the night (even the open bar) -- which he can definitely afford after putting together the largest contract in the history of pro sports.