Billy Arnold Muffett (September 21, 1930 – June 15, 2008) was an American professional baseball player and coach.

He pitched in the Major Leagues for all or parts of six seasons (1957–1962) for the St. Louis Cardinals, San Francisco Giants and Boston Red Sox.

In his playing days, he stood 6 feet 1 inch (1.85 m) tall, weighed 198 pounds (90 kg), and threw and batted right-handed.

[1] Muffett came to the major leagues with St. Louis in 1957 and fashioned his best overall season, winning three of five decisions, posting an earned run average of 2.25 and notching eight saves.

After retiring as a player, Muffett was a longtime MLB pitching coach for the Cardinals, California Angels and Detroit Tigers between 1967 and 1994, as well a minor league instructor.