Michael Constantine (born Gus Efstratiou (Ευστρατίου); May 22, 1927 – August 31, 2021) was an American actor. He is most widely recognized for his portrayal of Kostas "Gus" Portokalos, the Windex bottle-toting Greek father of Toula Portokalos (Nia Vardalos), in the film My Big Fat Greek Wedding (2002).

Earlier, he earned acclaim for his television work, especially as the long-suffering high school principal, Seymour Kaufman, on ABC's comedy-drama, Room 222, for which he won the Primetime Emmy Award for Outstanding Supporting Actor in a Comedy Series in 1970; he was again recognized by the Emmy Awards, as well as the Golden Globe Awards, the following year. After the conclusion of Room 222, Constantine portrayed night court magistrate Matthew J. Sirota on the 1976 sitcom Sirota's Court, receiving his second Golden Globe nomination. Constantine reprised his role as Gus Portokalos in My Big Fat Greek Wedding 2 (2016).