Karel Ardelt (, 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 Jià ÂàKodl) but did not play.
Ardelt competed for Czechoslovakia in two events in tennis at the 1920 Summer Olympics: singles and doubles (with Ladislav à ½emla).
In the Davis Cup, he represented Czechoslovakia and lost five times.