Kiara Mia is a porn legend ... not just for her work on-screen but for pulling Jimmy Garoppolo, one of the biggest stars in pro sports -- and now she's revealing her secrets!

Remember, it was Mia -- a 2-time AVN Award "Best M.I.L.F." nominee -- who famously went out on a date with Jimmy G back in July 2018 ... right after he signed his massive $137 mil contract with the 49ers.

And, now that Jimmy is CRUSHING it, Mia wants everyone to know she was the secret to his success!!

"I declared that they were going to make it to the Super Bowl," Kiara tells us at LAX ... "He's phenomenal, he's talented, he's a born star!"

What's funny is when we spoke with Kiara right after the date, she predicted greatness back then too ... saying, "Everything I touch turns to gold!"

Of course, the Niners ended up going 4-14 last season ... but NOW, they're 11-2 and sitting pretty at the top of the NFC East ... so maybe Kiara was right all along!!