William Earl Casper, Jr. (born June 24, 1931) is an American professional golfer who was one of the most prolific tournament winners on the PGA Tour from the mid 1950s to the mid 1970s.

Casper was born in San Diego, California. His father started him in golf at age five. He turned professional in 1954.

Casper had 51 PGA Tour wins in his career, placing him seventh on the all time list. His victories helped him finish third in McCormack's World Golf Rankings in 1968, 1969 and 1970, the first three years they were published. He won three major championships: the 1959 and 1966 U.S. Opens, and the 1970 Masters Tournament. He was the PGA Tour Money Winner in 1966 and 1968. He was PGA Player of the Year in 1966 and 1970. Casper won the Vardon Trophy for lowest scoring average five times: 1960, 1963, 1965, 1966, and 1968. He was a member of the United States team in the Ryder Cup 8 times—in 1961, 1963, 1965, 1967, 1969, 1971, 1973, 1975, and a non-playing captain in 1979. Casper has scored the most points in the Ryder Cup by an American player.