BMX bike legend Dave Mirra -- who once had the record for the most X Games medals -- has died of an apparent suicide ... TMZ Sports has learned.
Cops say the 41-year-old's body was found in his truck with an apparent self-inflicted gunshot wound to the head.
Mirra hosted 2 seaosns of "Real World/Road Rules Challenge" on MTV -- and was the namesake of several BMX video games.
Mirra also drove for Subaru rally car racing team.
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