John Rikard Dempsey (born September 13, 1949) is an American former professional baseball player. He played for 24 seasons as a catcher in Major League Baseball from 1969 to 1992, most prominently for the Baltimore Orioles where he played for 10 years and was a member of the 1983 World Series winning team. Dempsey was known for being one of the best defensive catchers of his era. In 1997, he was inducted into the Baltimore Orioles Hall of Fame.

Dempsey was selected by the Minnesota Twins in the 15th round of the 1967 Major League Baseball draft out of Crespi Carmelite High School. He spent two seasons in the minor leagues.

Dempsey made his major league debut late in the 1969 season for the division winning Twins managed by Billy Martin, however he didn't qualify for the postseason roster. Dempsey spent a few more seasons shuttling between the Twins and their minor league teams, before being traded to the New York Yankees for Danny Walton on October 31, 1972.

During his tenure with the Yankees, he served as a reserve catcher to Thurman Munson, and received tutoring from Yankees coach and former catching standout Jim Hegan. He was involved in a fight with teammate Bill Sudakis in the lobby of The Pfister Hotel while the ballclub was checking in on September 29, 1974. It was the culmination of an unpleasant conversation between the two players on a one-hour flight which was delayed for three hours at Cleveland Hopkins International Airport. The Yankees had swept a four-game series from the Indians and were still in contention for the American League East title with two games remaining in the regular season.

After three and a half seasons with the Yankees, the Baltimore Orioles acquired Dempsey along with Scott McGregor, Tippy Martinez, Rudy May, and Dave Pagan for Ken Holtzman, Doyle Alexander, Elrod Hendricks, Grant Jackson, and Jimmy Freeman at the trade deadline on 15 June 1976. He, McGregor and Martinez became part of a nucleus that enabled the Orioles to continue as perennial contenders for the next decade.

For the next ten and a half seasons, Dempsey was the Orioles' starting catcher. He became known for his exceptional ability to handle pitching staffs, his strong throwing arm, and for his agility behind home plate. In 1979, the Orioles defeated the California Angels in the 1979 American League Championship Series to reach the World Series. In the 1979 World Series, the Orioles won three of the first four games against the Pittsburgh Pirates and seemed to be on the verge of winning the championship, when the Pirates, led by Willie Stargell, rebounded to win the final three games. It was one of Dempsey's greatest disappointments of his playing career.

In 1983, the Orioles won the American League Eastern Division pennant, then defeated the Chicago White Sox in the 1983 American League Championship Series, before winning the 1983 World Series against the Philadelphia Phillies. Dempsey posted a .385 batting average along with a .923 slugging percentage in the five-game series, and won the World Series Most Valuable Player Award, one of six catchers to have won the award.

In 1987, Dempsey became a free agent and signed a contract to play for the Cleveland Indians. After only one season with the Indians, he became a free agent once again and signed with the Los Angeles Dodgers, where he would be a member of another World Series-winning team in 1988, this time as a backup catcher to Mike Scioscia. When Scioscia was injured during Game 4 of the World Series, Dempsey took over behind the plate for the remainder of the Series, collecting an RBI double in Game 5. While playing for the Dodgers in 1990, he became involved in a brawl with Phillies' center fielder Lenny Dykstra, who took exception to Dempsey's "buttering up" the home plate umpire. Anticipating something happening when Dysktra came closer to him, Dempsey promptly punched him with his catcher's glove. He was suspended for one game. After three seasons with the Dodgers, he played one season with the Milwaukee Brewers, before returning to the Baltimore Orioles for his final season in 1992.