Thomas Austin Preston Jr., known as Amarillo Slim, was an American professional gambler known for his poker skills and proposition bets. He won the 1972 World Series of Poker (WSOP) Main Event and was inducted into the Poker Hall of Fame in 1992.

The 1972 World Series of Poker (WSOP) was a series of poker tournaments held during early May 1972 at the Binion's Horseshoe in Las Vegas, Nevada. It was the 3rd annual installment of the World Series of Poker, and also the 2nd one to feature the freezeout structure. In comparison with the previous year's series, the number of events was cut back and the buy-ins were raised, resulting in 1 preliminary event and the Main Event both having the same buy-in of $10K. The preliminary event featured 5-card stud poker and was won by Bill Boyd, the same man who won the 1971 5-card stud preliminary event. The previous years' double champion Johnny Moss was defeated early in the main event and Thomas "Amarillo Slim" Preston went on to win the tournament after a series of deals.