Harry Duquesne "Duke" Markell (born Makowsky, August 17, 1923 – June 14, 1984) was a French-born professional baseball player, a right-handed pitcher whose career extended from 1945–1957, almost exclusively in minor league baseball. He appeared in five Major League games for the St. Louis Browns in the closing weeks of the 1951 season. Born in Paris, Markell stood 6 feet 1 inch (1.85 m) tall and weighed 209 pounds (95 kg).
Markell was in his seventh pro season when the Browns gave him his MLB opportunity. Although he had lost 19 games that summer for the Oklahoma City Indians of the Double-A Texas League, he had compiled a good 2.77 earned run average. Markell earned both of his Major League decisions in his two starting assignments. In his first, on September 16 at Shibe Park, he allowed seven hits (including home runs by Gus Zernial and Eddie Joost) and seven earned runs to take the loss in a 7–1 victory by the Philadelphia Athletics. In his second start on September 27, however, he threw a complete game, 7–4 victory over the Detroit Tigers at Sportsman's Park, outpitching veteran Tiger right-hander Fred Hutchinson. Although he gave up another homer, this time to Johnny Groth, Markell scattered eight hits and only three runs were earned.
Altogether, he gave up 25 hits and 20 bases on balls, striking out ten, in 21⅓ innings of big league action. After his brief trial with the Browns, Markell returned to the minor leagues, where he appeared in 508 games pitched and compiled a 154–142 record. In the early 1960s, the retired Jewish major league pitcher played outfield for The Free Sons of Israel lodge softball team "Mt. Horeb." He was a regular on the team and played on the Randall's Island softball fields in New York City.