The
World Series of Poker (
WSOP) is a series of
poker tournaments held annually in
Las Vegas and, since 2005, sponsored by
Caesars Entertainment (known as Harrah's Entertainment until 2010). It dates its origins to 1970, when
Benny Binion invited seven of the best-known poker players to the
Horseshoe Casino for a single tournament, with a set start and stop time, and a winner determined by secret ballot.