Harold Patrick Kelly (July 30, 1944 – October 2, 2005) was an American professional baseball player who played in Major League Baseball (MLB) as an outfielder from 1967 to 1981 with the Minnesota Twins, Kansas City Royals, Chicago White Sox, Baltimore Orioles and the Cleveland Indians. He batted and threw left-handed. His brother, Leroy, was a Pro Football Hall of Fame running back.

Born and raised in Philadelphia, Pennsylvania, Kelly was an "All Public" baseball player at Simon Gratz High School, honored with the Cliveden Award as Philadelphia's finest prep school athlete in 1962. Signed by the Twins that year, he spent the next several seasons in the minor leagues, debuting with the Twins in 1967. He played a handful of games for them in 1968, then was selected in the 1968 Major League Baseball expansion draft by the Royals, becoming an everyday player over the next two years with the fledgling franchise. Traded to the White Sox before the 1971 season, he spent part of 1971 in the minor leagues but got more playing time as a right fielder and designated hitter in the following years, reaching the All-Star Game for the only time in his career in 1973. Traded to the Orioles after the 1976 season, he received significant playing time in left field in 1977 and 1978, then served as a bench player the next two years. With a career-high .536 slugging percentage in 1979, Kelly helped the Orioles reach the MLB playoffs, appearing in the World Series, which Baltimore lost to the Pittsburgh Pirates in seven games. After one last season with the Indians in 1981, Kelly retired.

After becoming a born-again Christian in 1975, Kelly became very involved in Christian ministry. Under his influence, several of his Oriole teammates became Christians. Following his career, he became an ordained minister, serving at ministries in Baltimore and Cleveland until his death of a heart attack in 2005.

Harold Patrick Kelly was born on July 30, 1944, in Philadelphia, Pennsylvania, to parents Orvin and Argie Kelly. His parents had originally lived in South Carolina, but they had moved to the Nicetown neighborhood of northern Philadelphia in the 1920s, when Orvin was hired by a steel company. Pat was one of nine children, though he never met two of his siblings who died in 1940 because of rheumatic fever. He recalled, "My father worked for $12 a week to serve nine kids and put food on the table. He would wake up at four in the morning and it would be freezing cold outside. He would go in a pickup truck with no heat some 30 miles and work all day, but he went with God in his heart."

A faithful Baptist family, the Kellys attended Sunday school each week. They were also an athletic family; Leroy, Pat's older brother by two years and the closest in age to him, succeeded Jim Brown as the Cleveland Browns primary running back and was eventually inducted into the Pro Football Hall of Fame. Pat and Leroy competed all the time, which Pat credited for helping instill in him a competitive nature. He went to baseball games at Connie Mack Stadium growing up, and his favorite ballplayer was Jackie Robinson.

Kelly attended Simon Gratz High School, graduating in 1962. He was part of the "All Public" teams in both baseball and football. As a senior, he was honored with the Cliveden Award, presented to the finest Philadelphia prep school athlete. Though he would be an outfielder in the major leagues, Kelly was used as a pitcher in high school. After allowing home runs, he would often display a bad attitude, but the reprimands of coach Pete Lorenc eventually helped him overcome the habit. "When you played for him, the first thing you learned was discipline," Kelly said, observing its importance both in hitting and keeping a good attitude.

On September 11, 1962, Kelly signed his first professional baseball contract with the Minnesota Twins, who decided to use him as an outfielder. He split the 1963 season with the Erie Sailors of the Class A New York-Penn League and the Orlando Twins of the Class A Florida State League. Having grown up in Philadelphia, Kelly, who was black, was unused to dealing with segregation. At Orlando, though, he and his black teammates had to stay at a different hotel from the white players on the team. "I know those times were hard, but what always kept me going was what Jackie Robinson went through," he later recalled. In 69 games with Erie, he batted .283 with 50 runs scored, 70 hits, four home runs, and 30 runs batted in (RBI). With Orlando in 49 games, he batted .242 with 27 runs scored, 28 hits, no home runs, and 26 RBI.

Kelly spent most of 1964 with the Wisconsin Rapids Twins of the Class A Midwest League. In 104 games, he ranked among the league leaders with a .357 batting average (third, behind Dave May's .368 and Ed Moxey's .362), 138 hits (third, behind May's 166 and John Matias's 151), 26 doubles (tied with May, Eusebio Rosas, and David Burge for the league lead), 16 home runs (third, behind Rene Lachemann's 24 and Chuck Gross's 18), and 70 RBI (eighth). He also played 18 games with the Wilson Tobs of the Class A Carolina League, batting .245 with eight runs scored, 12 hits, no home runs, and eight RBI.