Jonathan Reid Cornelius (born June 2, 1970) is an American former professional baseball pitcher.

He played in Major League Baseball (MLB) for the Montreal Expos, New York Mets, and Florida Marlins.

He planned to play college baseball at Mississippi State but chose instead to begin a professional career after being taken in the eleventh round of the 1988 Major League Baseball draft by the Montreal Expos and receiving a signing bonus of $225,000 (equivalent to $580,000 in 2023).

[2] He began his professional career with the Rockford Expos of the Midwest League.

[4] Cornelius was named as the pitching coach for the Jupiter Hammerheads of the Miami Marlins organization for the 2019 season.