Gregory O'Neil McCarthy (born October 30, 1968) is an American former professional baseball relief pitcher.

Since his playing career ended, McCarthy has coached in the Netherlands and in baseball clinics and academies.

On February 17, 2009, he was hired to be the head coach of the Mosquito Athletics Attnang-Puchheim in the Austrian Baseball League.

[1] Greg McCarthy graduated from Central High School in Bridgeport, Connecticut[2]

This biographical article relating to an American baseball pitcher born in the 1960s is a stub.