William Llewellyn may refer to:
Thank you for reading this post, don't forget to subscribe!- Sir William Llewellyn (painter), Welsh painter
- William Llewellyn (bishop), Church of England bishop
- William Llewellyn (priest), Anglican priest
- William H. H. Llewellyn, member of the New Mexico House of Representatives
- Willie Llewellyn, Welsh rugby union player
- William Llewellyn (died 1902), Formerly missing Welsh person