Joseph Patrick Mauer (born April 19, 1983) is an American former professional baseball catcher and first baseman who spent his entire 15-year Major League Baseball (MLB) career with the Minnesota Twins. Regarded as one of the greatest contact hitters at the catcher position in his prime, Mauer is the only catcher in MLB history to win three batting titles, and the only catcher to ever win a batting title in the American League (AL). Internationally, Mauer represented the United States.

Selected by the Twins with the first overall pick of the 2001 MLB draft, Mauer received six All-Star selections, won three consecutive Gold Glove Awards (2008–2010), five Silver Slugger Awards (including three in a row), and the 2009 AL Most Valuable Player (MVP) Award. As of 2025^[update], he is the most recent catcher to win the MVP award in the American League, and one of only two catchers to win an MVP in the 21st century, along with Buster Posey. In 2024, Mauer was inducted into the Baseball Hall of Fame in his first year of eligibility.

Mauer played football, basketball, and baseball for St. Paul's Cretin-Derham Hall Raiders. In his senior year, he became the only athlete ever to be selected as the USA Today High School Player of the Year in football (quarterback, 2000) and baseball (catcher, 2001).

In December 2009, Sports Illustrated magazine included Mauer in its article on ten "signature" moments in U.S. high school sports in the 2000–2009 decade, referring to his selection by the Minnesota Twins as the first pick in the 2001 Major League Baseball draft.

Mauer attended the same high school as Baseball Hall of Famer and former Milwaukee Brewer Paul Molitor, who later became his major league manager with the Twins. Molitor has said that Mauer "has the best swing he had ever seen". Jim O'Neill, Mauer's baseball coach at Cretin-Derham Hall, said his former student "has been groomed for this job since he was a little boy. Mauer's dad, Jake, created a contraption for Joe he later named the 'Quickswing.' The device dropped balls down a tube from eye level and released them at waist level." Mauer had been asked to leave his T-ball league at the age of four, because he was hitting the ball too hard for the other players. "Another guy that came from Cretin-Derham Hall, Paul Molitor, was very similar, [and] had a good short swing," O'Neill said. "And they're both able to wait on the ball so long because they don't have the big swing. Like anything, you keep simple and keep it small or short, there's not a lot of holes in it and not a lot of room for errors."

A stand-out in baseball, Mauer struck out only once during his four-year high school career (though he did strike out in the All-Star game his senior year which isn't included in his overall stats). He hit .605 during his senior season. Years later, Mauer laughingly told an interviewer: "I can remember the time I did strike out. It was junior year, and it was in the state tournament. I came back to the bench and everybody thought something was wrong with me." Mauer's high school batting average exceeded .500 every year. He also set a Minnesota high school record and tied the national preps mark by hitting a home run in seven consecutive games. Mauer caught for the Team USA Junior National team from 1998 to 2000 and hit .595 during his final year on the team. He was voted best hitter at the World Junior Baseball Championship in Canada in 2000. In 2001, Mauer was voted the United States District V Player of the Year.

Mauer averaged more than 20 points a game as a point guard for Cretin-Derham Hall. He was also named to the All-State team during his final two years on Cretin-Derham's basketball team.

Mauer had an accomplished high school football career. In 2000, he appeared in the Faces in the Crowd section in Sports Illustrated. During his senior season as the Raiders' quarterback, Mauer completed 178 of 269 passes (66% completion percentage), for 3,022 yards, 41 touchdowns and five interceptions. He finished his two-year career as a starter with 5,528 yards and 73 touchdowns, leading the Raiders to two consecutive Class 5A State Championship Game appearances and winning the title in 1999, the Raiders' first.