Don James Larsen (August 7, 1929 – January 1, 2020) was an American professional baseball pitcher. During a 15-year Major League Baseball (MLB) career, he pitched from 1953 to 1967 for seven different teams: the St. Louis Browns / Baltimore Orioles (1953–54; 1965), New York Yankees (1955–1959), Kansas City Athletics (1960–1961), Chicago White Sox (1961), San Francisco Giants (1962–1964), Houston Colt .45's / Astros (1964–65), and Chicago Cubs (1967).

Larsen pitched the sixth perfect game in MLB history, doing so in Game 5 of the 1956 World Series. It is the only solo no-hitter and perfect game in World Series history and is one of only three no-hitters in MLB postseason history (the others being Roy Halladay's in 2010 and the combined Houston Astros no-hitter in 2022). He won the World Series Most Valuable Player Award and Babe Ruth Award in recognition of his 1956 postseason.

Larsen was born in Michigan City, Indiana. Larsen's family moved to San Diego, California, in 1944, where his mother became a housekeeper and his father worked as a department store salesman. Larsen attended Point Loma High School where he was a member of the basketball and baseball teams. He was selected for the All-Metro Conference team as a basketball player, and was offered several college scholarships to play basketball.

In baseball, Larsen's ability for the local American Legion team caught the attention of St. Louis Browns scout Art Schwartz. Schwartz signed Larsen to a contract to play for one of the Browns' minor league teams in 1947, with Larsen receiving an $850 signing bonus (about $11,652 as of September 2023). Larsen, on why he signed with the Browns over attending college, later said that he was "never much with the studies."

Larsen started his career with the Aberdeen Pheasants of the Class-C Northern League in 1947, appearing in 16 games. He had a 4–3 win–loss record and a 3.42 earned run average (ERA). The next season with Aberdeen, he won 17 games and had a 3.75 ERA in 34 games. Larsen started the 1949 season pitching for the Globe-Miami Browns of the Class-C Arizona–Texas League, before he moved up the minor league hierarchy, playing for the Springfield Browns in the Class-B Illinois–Indiana–Iowa League, and the Wichita Falls Spudders of the Class-B Big State League for the first half of the 1950 season. Larsen was promoted to the Wichita Indians of the Class-A Western League in the second half of the 1950 season. With the Indians, Larsen had a 6–4 record with a 3.14 ERA in 21 games. In 1951, Larsen was drafted to the United States Army for the Korean War. He spent the next two years in the Army, working in a variety of non-combat jobs. He was discharged from the Army in 1953 and made the St. Louis Browns roster prior to the beginning of the season.

Larsen made his Major League Baseball (MLB) debut with a start against the Detroit Tigers on April 17, 1953. He pitched five innings, giving up three earned runs, while striking out three in a no decision in an 8–7 Browns win. He had his first career win a little less than a month later, on May 12, against the Philadelphia Athletics, pitching 7+2⁄3 innings and giving up one earned run in a 7–3 win. For his rookie season, Larsen finished with a 7–12 record, 4.16 ERA and 96 strikeouts in 38 games, 22 of them starts. He finished first on the team in innings pitched (192+2⁄3) and complete games (7) and second on the team in strikeouts. Larsen also allowed the most hits with 202, and earned runs (89) on the squad. He also broke a major league record for pitchers by having seven consecutive hits at one point. He batted .284 with 3 home runs in 81 at bats in his rookie year.

The Browns relocated to Baltimore for the 1954 season, becoming the Baltimore Orioles. In 1954, Larsen went 3–21 with a 4.37 earned run average and 80 strikeouts in 29 games. It was the fewest wins by a pitcher with at least 20 losses since 1916; and no 20-loss pitcher has had as few wins since then, a span of 110 years. He led the major leagues in losses and finished third in the league in earned runs allowed (98). The Orioles won only 54 games that season, while having 100 losses, and finished the season in seventh place. Two of Larsen's three wins were against the New York Yankees, including a 10–0 shutout on July 30, his last win of the season. His other victory was against the Chicago White Sox on May 30.

In 1954, the New York Yankees, despite winning 103 games, finished second behind the Cleveland Indians in the American League. Yankees general manager George Weiss blamed the age of their pitching staff for their performance. The Yankees’ “Big Three” pitching staff of the late 1940s and early 1950s, Vic Raschi, Ed Lopat and Allie Reynolds, were in their late thirties, and wearing down. Raschi was traded to the Cardinals prior to the season, Reynolds retired because of a back injury and Lopat was ineffective and retired within a year. Two other pitchers in the staff, Johnny Sain and Tommy Byrne were also near the end of their careers. Desperate for young starting pitching behind staff ace Whitey Ford and promising starter Bob Grim, Weiss managed to find a trade partner with the Orioles. At the end of the season, Larsen was traded by the Baltimore Orioles as part of a 17-player trade, with Billy Hunter, Bob Turley and players to be named later to the Yankees for, most prominently, catcher Gus Triandos, and outfielder Gene Woodling. When the trade was announced Turley was considered the key player in the trade. During the 1954 season, Turley had a 14–15 record, and some observers considered Turley to have the "liveliest fastball" in the league. However, Weiss and Yankees manager Casey Stengel thought that Larsen had the most potential out of the two, having been impressed with Larsen's performance against the Yankees and demanded that he be included in the trade.