Casa Batlló (Catalan pronunciation: [ˈkazə βəˈʎːo] ) is a building in the center of Barcelona, Spain. It was designed by Antoni Gaudí, and is considered one of his masterpieces. A remodel of a previously built house, it was redesigned in 1904 by Gaudí (but the actual construction works hadn't begun at this point) and has been refurbished several times since. Gaudí's assistants Domènec Sugrañes i Gras, Josep Canaleta and Joan Rubió also contributed to the renovation project.
The local name for the building is Casa dels ossos (House of Bones), as it has a visceral, skeletal organic quality. It is located on the Passeig de Gràcia in the Eixample district, and forms part of a row of houses known as the Illa de la Discòrdia (or Mansana de la Discòrdia, the "Block of Discord"), which consists of four buildings by noted Modernista architects of Barcelona.