William "Billy" Mellor (date and place of birth unknown) was a footballer who played as a defender. Having played as a young amateur for teams in Sheffield, Mellor was spotted by Sheffield United and offered a professional contract in the summer of 1892. United had been accepted into Football League Division Two for the following season and Mellor struggled to meet the standard required, making only four league appearances for the club. Mellor then dropped out of league football and had spells with Oldham County, Swindon Town and Wigan County before finishing his career with Darwen.