Frank Edward Thomas Jr. (born May 27, 1968), nicknamed "the Big Hurt", is an American former professional baseball first baseman and designated hitter in Major League Baseball (MLB). He played for three American League (AL) teams from 1990 to 2008, all but the last three years with the Chicago White Sox. A five-time All-Star, he is the only player in major league history to have seven consecutive seasons (1991–1997) with at least a .300 batting average, 100 runs batted in (RBI), 100 runs scored, 100 walks, and 20 home runs. Thomas also won the AL batting title in 1997 with a .347 mark. Thomas is a two-time AL MVP and won a World Series in 2005 although he was injured during the regular season and World Series.

Drafted seventh overall by the White Sox in the 1989 MLB draft, Thomas made his major league debut the following year and immediately impressed with his hitting ability. Thomas was named the AL's Most Valuable Player (MVP) by unanimous vote in 1993. That year, he became the first White Sox player to hit 40 home runs and led the team to a division title. He repeated as MVP in the strike-shortened 1994 season, batting .353 and leading the league in slugging percentage and runs. Following two sub-par seasons, Thomas lost a close MVP vote in 2000 despite posting career highs of 43 home runs and 143 RBI. Still, he was named AL Comeback Player of the Year, and Chicago finished with the AL's best record. Later in Thomas's career, a variety of foot injuries and minor ailments reduced his productivity and often limited him to a designated hitter role. In 2005, his final season in Chicago, he was limited to only 34 games after starting the year on the disabled list and then fracturing a bone in his foot close to where it was surgically repaired the previous off-season. He was unable to play in the post-season while the White Sox won the World Series that year. Thomas spent the final three years of his career with the Oakland Athletics and Toronto Blue Jays, with whom he hit his 500th home run.

By the end of his career, Thomas was tied for eighth in AL history for home runs (521), ninth for RBI (1,704), and sixth for walks (1,667). Among players with at least 7,000 at bats in the AL, he ranked eighth in slugging average (.555) and ninth in on-base percentage (.419). With a .301 lifetime batting average, he became the seventh player in history to retire with at least a .300 average and 500 home runs. He holds White Sox franchise records for career home runs (448), RBI (1,465), runs (1,327), doubles (447), extra base hits, walks (1,466), slugging average, (.568) and on-base percentage (.427). The White Sox retired Thomas's uniform number 35 in 2010 and unveiled a statue of him at U.S. Cellular Field in 2011. Thomas was elected to the Baseball Hall of Fame in 2014 in his first year of eligibility—the first White Sox star to achieve that distinction.Thomas was one of the few major league stars who never fell under suspicion during the performance-enhancing drugs controversies of the late 1990s. An advocate for drug testing as early as 1995, he was the only active player who agreed to be interviewed for the Mitchell Report in 2007.