Castilian or Castillian may refer to:

• Castile, a historic region of the Iberian peninsula
  • Castilian people, an ethnic group from Castile
  • Castilian languages, a branch of the West Iberian languages consisting of all linguistic varieties descended from Old Latin
    • Spanish language, a Romance language that originated in Castile
      • Castilian Spanish, a variety of Peninsular Spanish spoken in Spain
  • Crown of Castile, a former state on the Iberian Peninsula
  • Kingdom of Castile, a former kingdom on the Iberian Peninsula
  • Castile and León, an autonomous community of Spain
  • Castile–La Mancha, an autonomous community of Spain
• SS Castilian, a 1919 British ship
• The Castilian, a 1963 film
• Castilian War, a war between several sultanates and the Spanish Empire.

• Castile (disambiguation)
• Nationalities of Spain (disambiguation)