Alcazar, Alcázar (Spanish), Alcácer (Portuguese), Alcàsser (Catalan), are all transliterations of the Arabic word al qasr (القصر), meaning "the castle", "palace" or "fortress". It may refer to:

• Alcázar, a type of palace or fortress in Spain, and sometimes in Portugal and Latin America:
  • Alcázar of Segovia, in Castile and León, Spain
  • Alcázar of Toledo, in Castile-La Mancha, Spain
  • Alcázar of Jerez de la Frontera, in Andalusia, Spain
  • Alcázar of Salamanca, in Castile and León, Spain
  • Alcázar of Guadalajara, in Castile-La Mancha, Spain
  • Alcázar of Madrid, Spain
  • Alcázar of Seville, in Andalusia, Spain
  • Alcázar Genil (or Alcázar of Granada), in Andalusia, Spain
  • Alcázar de los Reyes Cristianos (or Alcázar of Córdoba), in Andalusia, Spain
  • Castle of Burgos, formerly an Alcázar
  • Alcázar of Úbeda, Jaén, in Andalusia, Spain
  • Alcázar de Don Diego Colón, former residence of Christopher Columbus's son Diego in Santo Domingo, Dominican Republic
  • Castillo Alcázar de Segorbe, disappeared.
  • Alcázar de Plasencia, was demolished.
  • Alcázar Real de Ciudad Real, disappeared.

An alcázar is a type of Moorish castle or palace in Spain and Portugal built during Muslim rule, mostly between the 8th and 15th centuries. Many cities in Spain have an alcázar. Palaces built in the Moorish style after the expulsion of the Moors from Spain are often referred to as alcazars as well.