William, Willie, Bill, or Billy Ritchie may refer to:
Law and politics Sir William Johnstone Ritchie (1813–1892), Chief Justice of Canada William Ritchie (barrister) (1817–1862), English Advocate-General of Bengal
William Gordon Ritchie (1918–1998), Canadian politician Bill Ritchie (politician) (1927–2014), Canadian politician
Sports William Ritchie (rugby union) (1882–1940), Scottish international rugby union player Willie Ritchie (golfer) (1884–1966), Scottish golfer Willie Ritchie (1891–1975), American boxer William E. Ritchie (1871-1943), American trick bicyclist William Ritchie (footballer) (1895–1965), Scottish footballer Billy Ritchie (1936–2016), Scottish footballer
Others William Ritchie (moderator) (1758–1830), Moderator of the General Assembly of the Church of Scotland William Ritchie (editor) (1781–1831), Scottish journalist William Ritchie (physicist) (1790–1837), Scottish physicist William Thomas Ritchie (1873–1945), Scottish cardiologist Bill Ritchie (1931–2010), Scottish cartoonist Billy Ritchie (musician) (born 1944), British keyboard player and composer