Ernest Gerald Koob (September 11, 1892 – November 12, 1941) was an American professional baseball player who played pitcher in the Major Leagues from 1915 to 1919 for the St. Louis Browns.

The very next day, his teammate Bob Groom also no-hit the White Sox, 3–0 in the second game of a doubleheader; to date, Koob and Groom are the only teammates to pitch no-hitters on consecutive days.

An obituary published in the November 1941 issue of "The Sporting News" contained statements which complement and to some extent contradict the above information.

It states that Mr. Koob was born in St. Louis in 1894; that he died in the Mount St. Rose Sanatorium (St. Louis) on 12 November 1941, of a lung ailment; that he played baseball under the name "Smith" while attending Kalamazoo State College; that he served in the US Army during The Great War; and that he played with the Browns until 1920.

This biographical article relating to an American baseball pitcher born in the 1890s is a stub.