Von Miller is going on the offensive -- trying to block a woman from releasing a sex tape shot in Cancun ... and claiming she's demanding $2.5 MILLION or else.
The Denver Broncos superstar filed legal docs in L.A. County Superior Court under the pseudonym "Doe" -- but multiple sources confirm "Doe" is Miller.
In fact, he's described in the legal docs as "one of the most talented people at his craft in the U.S. and the world."
In the docs, Miller says he met a woman named Elizabeth Ruiz during a trip to Mexico in June 2016 -- and the two had sex while they were alone indoors.