Karel Ardelt (Czech pronunciation: [ˈkarɛl ˈardɛlt], 28 January 1889 – 14 February 1978) was a Czech tennis player. As a player for Bohemia, he was entered in two events in tennis at the 1912 Summer Olympics: outdoor singles and outdoor doubles (with Jiří Kodl) but did not play. Ardelt competed for Czechoslovakia in two events in tennis at the 1920 Summer Olympics: singles and doubles (with Ladislav Žemla). In the Davis Cup, he represented Czechoslovakia and lost five times.