Mark Philip Schaeffer (born June 5, 1948) is an American former professional baseball player. He played in Major League Baseball as a pitcher for the San Diego Padres in 1972. He batted and threw left-handed.

Schaeffer was born in Santa Monica, California and attended Grover Cleveland High School in Reseda, California. He was drafted by the Boston Red Sox in the second round of the 1966 Major League Baseball draft. Schaeffer made his major league debut on April 18, 1972 at the age of 23 with the San Diego Padres.