Harry Tressler is a fictional character from the BBC medical drama Holby City, played by Jules Knight. He first appeared in the fifteenth series episode "The More Deceived", broadcast on 14 May 2013. Harry was introduced as a CT1, later progressing to CT3. Knight's casting was announced in January 2013. He auditioned four times, with the producers taking two and a half months to choose him for the part. To help prepare for the role, Knight shadowed a surgeon and watched a laparotomy. In February 2015, it was announced that Knight had quit the show in order to concentrate on the release of his first solo record. Harry departed during the seventeenth series on 14 April 2015.

Julian "Jules" Knight is an English actor and singer. He is best known for being a member of the British vocal group Blake and his portrayal of Harry Tressler in the medical drama Holby City. He left Blake in January 2013 and first appeared in Holby City as doctor Harry Tressler on 14 May 2013. Knight left Holby City on 14 April 2015.