William Joseph Buckner (born December 14, 1949 in Vallejo, California) was a Major League Baseball player who, despite a respectable 20-year career, is best known for a groundball that skittered between his legs in Game 6 of the 1986 World Series.

With a three games to two lead in the series, the Boston Red Sox had just squandered their lead for the third time in the game, this time on a wild pitch. It was the bottom of the tenth inning, October 25, 1986, at Shea Stadium, two outs, a runner on second, the score tied, Mookie Wilson of the New York Mets at the plate. After fouling off close to a dozen pitches, Wilson hit a routine ground ball to Buckner at first base. The ball, which had taken a deadening bounce on the dirt, rolled under Buckner's glove, through his legs and into right field, allowing the winning run to score. It capped an astonishing comeback for the Mets, however, it did not (as is often misremembered) end the World Series. The Met victory, in fact, forced a seventh game, which was played two nights later and subsequently won by the Mets.

Although many factors can be cited as to why the Red Sox lost the 1986 World Series, the "Buckner Ball" remains the popular focus of the blame. Moreover, the "Buckner Ball" has been added to the lore of the Curse of the Bambino.

According to a popular Bostonian joke, the distraught Buckner threw himself in front of a locomotive in grief after his fielding error. The train passed between his legs.

The "Buckner Ball" was later auctioned for $93,000. The high bidder was Charlie Sheen. The ball is now in the collection of Seth Swirsky, who refers to it as the "Mookie Ball."

Buckner played his first major league game in 1969 (at the age of 19) and his last game in 1990 (at the age of 40).

In 2,517 games, Buckner accumulated 2,715 hits in his career, including 498 doubles. He won the National League batting title in 1980, and was an All-Star in 1981. He played 1,555 regular season games at first base and made only 128 errors in 13,901 possible chances, but he will always be remembered for one error he made in the World Series.

Boston band Slide named their debut album Forgiving Buckner.