Unseen Gracie Challenge Fights

The Gracie challenge was an open invitation issued by some members of the Brazilian Gracie family, known for their Brazilian jiu-jitsu (BJJ) mastery, to martial artists of other styles to fight them in a vale tudo match.
A precursor to the Ultimate Fighting Championship (UFC), the purpose of these challenges was to prove the effectiveness of the Gracie style of BJJ.
Challenges have been issued since Carlos Gracie first made one in the 1920s with some becoming public events while others have remained private.