Walter A. Mayer (July 8, 1890 – November 18, 1951) was a backup catcher in Major League Baseball who played from 1911 through 1919 for the Chicago White Sox (1911–1912, 1914–1915), Boston Red Sox (1917–1918) and St. Louis Browns (1919). Listed at 5 ft 11 in (1.80 m), 168 lb., Mayer batted and threw right-handed. He was born in Cincinnati.
In a seven-season career, Mayer was a .193 hitter (53-for-274) with 22 runs and 20 RBI in 132 games, including 14 doubles, one triple, one stolen base, and a .303 on-base percentage. He did not hit a home run. In 112 catching appearances, he committed 17 errors in 553 chances for a .968 fielding percentage.
Mayer died in Minnetonka, Minnesota at age 61.