Willard Eben Mains (July 7, 1868 – May 23, 1923) was an American professional baseball pitcher.

He joined the National League at the age of 20 with the Chicago White Stockings and started two games in 1888, winning one and losing the other.

After that season, he did not return to the majors until 1891, when he pitched in 30 games, starting 23 of them, for the Cincinnati Kelly's Killers of the American Association.

He was not seen in the major leagues again until five years later when he surfaced for the 1896 Boston Beaneaters, with whom he pitched in eight games, winning three and losing two.

[1] Willard Mains had a long career in minor league baseball, where he had a record of 318 wins and 179 losses in 545 games.