Gregory Joseph O'Halloran (born May 21, 1968) is a Canadian former professional baseball catcher.

As a child, he thought of baseball simply as "something I did in the summer when I wasn't playing hockey.

At the time, he was the fourth player on their catching depth chart behind Pat Borders, Randy Knorr and Carlos Delgado.

His son, Connor, was selected by the Toronto Blue Jays in the fifth round of the 2023 Major League Baseball draft.

This biographical article relating to a Canadian baseball catcher is a stub.