Marcus Walter Walden (born September 13, 1988) is an American professional baseball pitcher in the Milwaukee Brewers organization. He has played in Major League Baseball (MLB) for the Boston Red Sox. He made his MLB debut during 2018 after a decade of minor and independent league baseball. He both throws and bats right-handed, and is listed at 6 feet 0 inches (1.83 m) and 195 pounds (88 kg).