Ralph Michael Caldwell (born January 22, 1949) is an American former professional baseball left-handed pitcher.

His Padres won‐lost record of 13–25 included a second full major‐league season in 1973 in which he was mostly a relief pitcher who went 5–14 with a 3.74 earned run average (ERA).

After just 14 games, the Reds traded him to the Milwaukee Brewers for minor leaguers Dick O'Keefe and Garry Pyka.

Caldwell was named the AL Comeback Player of the Year by The Sporting News and finished second in the Cy Young Award balloting to Ron Guidry.

Caldwell threw mainly a sinker and a regular fastball, relying on control and varying speeds of pitches to get outs.