K. C. Constantine (a pseudonym for Carl Constantine Kosak; born 1934) is an American mystery author.
Little is known about Kosak, as he prefers anonymity and has given only a few interviews. He was born in 1934 and served in the Marines in the early 1950s. He lives in Greensburg, Pennsylvania with wife Linda.
Other than that, information is sketchy. He may have been a minor league baseball player (some even suggest that Kosak is a pseudonym for former Major League baseball player Phil Rizzuto) and he may have studied at the University of Iowa's writers' program in the 1960s. Other evidence suggests he never got near a baseball and instead was a journalist at a western Pennsylvania newspaper.
Kosak continued to work a day job until 1993, when he lost his job and turned to writing full time. He worked for several years as an English teacher at Seton Hill University (then Seton Hill College) in Greensburg, where he taught creative writing and composition, until his refusal to complete his Master's degree prompted his dismissal.
His most famous creation is Mario Balzic, police chief in fictional Rocksburg, Pennsylvania. Rocksburg is a by-product of Kosak's hometown McKees Rocks, Pennsylvania. Kosak is much more interested in the people in his novels than the actual mystery, and his later novels become ever more philosophical, threatening to leave the mystery/detective genre behind completely.