Horst Käsler (18 April 1926 – 17 December 1987) was a German handball player, coach, and author.
Käsler had his greatest success as a player in the 1950s. In 1955 he led the German national team to a world championship in field handball.
After his career as a player, he coached at Berlin University and wrote several manuals on training tactics and conditioning for the game. On 1 October 1972, he succeeded Werner Vick as trainer of the German national team, a position he held until 1974.
In memory of his achievements, a sports hall in Berlin-Schmargendorf was named for him.