William "Billo" Rees (14 April 1899 – 1968) was a Welsh rugby union, and professional rugby league footballer who played in the 1920s and 1930s. He played club level rugby union (RU) for Amman United RFC, and representative level rugby league (RL) for Great Britain and Wales, and at club level for Swinton, as a stand-off, or scrum-half, i.e. number 6, or 7.