Masiulis is the masculine form of a Lithuanian family name. Its feminine forms are: Masiulienė (married woman or widow) and Masiulytė (unmarried woman). Notable people with the surname include:
Algimantas Masiulis (1931–2008), Lithuanian actor Artūras Masiulis (born 1980), Lithuanian basketball player Eligijus Masiulis (born 1974), Lithuanian politician Gytis Masiulis (born 1998), Lithuanian basketball player , Lithuanian knygnešys Laurynas Masiulis, baptismal name of Laurynas Gucevičius, 18th-century Lithuanian architect Tomas Masiulis (born 1975), Lithuanian basketball player