Alexander Dominick Mustaikis (March 26, 1909 – January 17, 1970) was a pitcher in Major League Baseball who played briefly for the Boston Red Sox during the 1940 season. Listed at 6 ft 3 in (1.91 m), 180 lb., Mustaikis batted and threw right-handed. He was born in Chelsea, Massachusetts.

In one season career, Mustaikis posted a 0–1 record with six strikeouts and a 9.00 ERA in six appearances, including one start, three games finished, and 15.0 innings of work.

Mustaikis died at the age of 60 in Scranton, Pennsylvania.