William Glen or Glenn may refer to:

• William Glen (geologist) (born 1932), American geologist and historian of science
• William Glen (poet) (1789–1826), Scottish poet
• William Glen (footballer) (1903–1981), Irish football player
• William Glenn (1914–2003), American cardiac surgeon
• William E. Glenn (1926–2013), American inventor
• William H. Glenn (1872–1940), American industrialist
• Billy Glenn (William Spiers Glenn, 1877–1953), New Zealand politician