Andrew Jackson Leonard (June 1, 1846 – August 21, 1903) was an Irish born professional baseball player of the 19th century, who played outfield and was also a utility infielder.

Born 1846 in County Cavan and raised in Newark, New Jersey, Leonard is commonly recognized as the first native of Ireland to play in the major leagues.

Leonard played five seasons in the amateur era of the National Association of Base Ball Players (NABBP), beginning in 1864 with the Hudson River club of Newburgh, New York, not far North of the metropolis.

He played nine of the next ten seasons as Harry Wright's regular left fielder, although as a right-handed thrower with early infield experience he filled in at second, third, and shortstop, too.

The limited statistical record shows that he was one of the strong supporting players during the Red Stockings innings, perhaps third behind George Wright and Waterman over the two seasons, but that may be said of a few others.

The other five regulars including Andy Leonard signed with Nick Young's Washington Olympics, an established club that also joined the new, entirely professional National Association (NA).

Andy Leonard lost his major league job in 1879 but returned to the infield in Rochester as a shortstop, in some ways the most demanding position, one always filled by George Wright on brother Harry's professional teams.