Karel Sys (14 February 1914 – 19 June 1990) was a Belgian boxer who having started his professional career at welterweight went on to become heavyweight champion of Europe on two occasions, winning the title in both 1943 and 1952.

Sys had continued to fight during the German occupation of Belgium during World War II and in 1945 he was arrested on charges of collaboration and felony.

[3] On his release he moved to Spain, where he hoped to revive his career, but after failing to get a Spanish licence turned to professional wrestling, using the name Van Will.

[4] He returned to Belgium and was able to resume his career in his home country, winning seven fights before taking on Hein ten Hoff at the Palais des Sports in January 1952 in an attempt to regain his European title.

After facing tax demands from the Belgian government relating to his boxing winnings dating back to the pre-war period, he returned to live in Argentina.