Luka Kovač is a fictional character from the NBC television series ER. The role was portrayed by Goran Višnjić from the sixth season episode, "Leave It to Weaver", which aired on September 30, 1999 until the thirteenth season episode, "The Honeymoon Is Over", which aired on May 17, 2007.
Višnjić appeared as a guest in seven episodes during the fourteenth season of the show, beginning with "Under the Influence" on October 25, 2007 and concluding with "The Chicago Way" on May 15, 2008. He returned to the show's fifteenth and final season for another guest appearance in "The Book of Abby", which aired on October 16, 2008.
Luka Kovač is an emergency room attending physician from Croatia.
He moves to the United States of America some time after that for a fresh start, but evidence he suffered from both survivor's guilt and PTSD soon emerge, largely in terms of his personal relationships. Višnjić himself named the character: name Luka in honour of his nephew, and surname Kovač of his best friend.