William Clark Jr. (born March 13, 1964) played first base from 1986 through 2000 for the San Francisco Giants, Texas Rangers, Baltimore Orioles, and St. Louis Cardinals. Clark was known by the nickname of "Will the Thrill." The nickname has often been truncated to simply, "The Thrill."

Clark played college baseball for the Mississippi State Bulldogs, where he won the Golden Spikes Award, and at the 1984 Summer Olympics before playing in the major leagues. Clark was a six-time MLB All-Star, a two-time Silver Slugger Award winner, a Gold Glove Award winner, and the winner of the National League Championship Series Most Valuable Player Award in 1989.

Clark has been inducted into the National College Baseball Hall of Fame, Mississippi Sports Hall of Fame, Louisiana Sports Hall of Fame, and Bay Area Sports Hall of Fame. His uniform number was retired by the Giants during the 2020 season. Clark continues to be active in baseball, serving as a Special Assistant in the Giants' front office.