Oscar De La Hoya said he can knock out Conor McGregor in 2 rounds ... and Conor McGregor says PROVE IT -- calling out the legend for a real-deal boxing match.

SO, WHAT ARE WE WAITING FOR?!? LET'S DO THIS!!!!

Here's how it all got started ... 47-year-old ODLH was asked about his chances against the 31-year-old UFC superstar earlier this week ... saying it would be a cakewalk.

"2 rounds," the Golden Boy told "The State of Combat" podcast. "Because one thing about me ... I went for the kill always."

"And look, Conor McGregor is – I love him in the Octagon. I respect him. I watch him all the time."

"But, the boxing ring is a whole different story. It’s a whole different story."

Conor -- who's always wanted a second shot at a boxing match following his loss to Floyd Mayweather in 2017 -- heard what ODLH had to say ... and he wants the legend to put his money where his mouth is ... IN THE RING!!!

"I accept your challenge, Oscar de la Hoya," Conor tweeted.

Now, Oscar (39-6) hasn't had a pro fight since losing to Manny Pacquiao in 2008 by a referee technical decision ... but the Golden Boy's confident he can shake off any ring rust against the 0-1 Conor.

Remember, ODLH made a similar threat to Conor back in 2017 ... saying he was in shape and ready to throw down with the Notorious.

There's only one way to find out -- PLEASE MAKE THIS HAPPEN.