"Two porn companies are going head-to-head in a ferocious battle to buy the rights to the Tupac Shakur sex tape ... and TMZ has learned the first bid is well into 6-figures.
Sources close to the person in possession of the tape tell us ... neither company has actually laid eyes on the footage ... but both sites are serious about acquiring the rights.
TMZ has confirmed ... one of the potential buyers is a site called YouPorn.com -- and YouPorn.com honcho Corey Price tells us the site has made an official offer to pay $150k for the tape.
According to sources, the person in possession of the tape believes the offer is "way too low" -- and is willing to hold out for more money.
We're told the seller has been in contact with a second, unidentified porn site, which has vowed to to beat the current offer -- but only if it can screen the footage first.
As TMZ first reported, the footage was shot in 1991... and it features the late rapper receiving oral sex from a woman while rapping, drinking and smoking a blunt at a house party.