Casa Batlló is a building in the center of Barcelona. 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 and has been refurbished several times after that. 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.
Like everything Gaudí designed, Casa Batlló is only identifiable as Modernisme or Art Nouveau in the broadest sense. In 2005, Casa Batlló became an UNESCO World Heritage Site among the other Works of Antoni Gaudí, and is visited by people from around the world.