David Paul Leonhard (born January 22, 1941) is a former pitcher in Major League Baseball who played from 1967 through 1972 for the Baltimore Orioles. Listed at 5' 11", 165 lb., Leonhard batted and threw right-handed. He attended Johns Hopkins University.
A native of Arlington, Virginia, Leonhard was signed by the Orioles as a free agent in 1963. He started his professional career with Class C Aberdeen Pheasants (1963–1964), and won the International League Pitcher of the Year Award while playing for the Rochester Red Wings in 1967, gaining a promotion to Baltimore late in the season.
In three games with the 1967 Orioles, Leonhard went 0-0 with a 3.14 ERA in 14 ⅓ innings of work. In 1968 collected a 7-7 record in a starting rotation that included Dave McNally (22-10), Jim Hardin (18-13) and Tom Phoebus (15-15), but with the emergence of Jim Palmer in 1969, he was relegated to the bullpen.
In a six-season career, Leonhard posted a 16-14 record with a 3.15 ERA in 117 appearances, including 29 starts, seven complete games, four shutouts and five saves, giving up 118 earned runs on 287 hits and 150 walks while striking out 146 in 337.0 innings.
Leonhard appeared in the 1969 and 1971 World Series (3.00 ERA in two games), and won a World Series ring in 1970 though he did not play in the Series. He also pitched with the Puerto Rican team in the 1971 Caribbean Series and for Triple-A Salt Lake City Angels in 1973.On May 6, Leonhard took a no-hitter into the seventh inning before Detroit Tigers outfielder Jim Northrup broke it up with a single after two outs. He had to conform with a one-hit shutout, 4–0 victory over Detroit at Memorial Stadium.
On May 30, he blanked the Chicago White Sox at Comiskey Park, 5–0, giving up just two singles to Luis Aparicio (4th inning) and Tommy McCraw (7th).