Modernisme (Catalan pronunciation: [muðərˈnizmə], Catalan for "modernism"), also known as Catalan modernism and Catalan art nouveau, is the historiographic denomination given to an art and literature movement associated with the search of a new entitlement of Catalan culture, one of the most predominant cultures within Spain. Nowadays, it is considered a movement based on the cultural revindication of a Catalan identity. Its main form of expression was Modernista architecture, but it also encompassed many other arts, such as painting and sculpture, and especially the design and the decorative arts (cabinetmaking, carpentry, forged iron, ceramic tiles, ceramics, glass-making, silver and goldsmith work, etc.), which were particularly important, especially in their role as support to architecture. Modernisme was also a literary movement (poetry, fiction, drama).

Although Modernisme was part of a general trend that emerged in Europe around the turn of the 20th century, in Catalonia the trend acquired its own unique personality. Modernisme's distinct name comes from its special relationship, primarily with Catalonia and Barcelona, which were intensifying their local characteristics for socio-ideological reasons after the revival of Catalan culture and in the context of spectacular urban and industrial development. It is equivalent to a number of other fin de siècle art movements going by the names of Art Nouveau in France and Belgium, Jugendstil in Germany, Vienna Secession in Austria-Hungary, Liberty style in Italy and Modern or Glasgow Style in Scotland.

Modernisme was active from roughly 1888 (the First Barcelona World Fair) to 1911 (the death of Joan Maragall, the most important Modernista poet). The Modernisme movement was centred in the city of Barcelona, though it reached far beyond, and is best known for its architectural expression, especially in the work of Antoni Gaudí, Lluís Domènech i Montaner and Josep Puig i Cadafalch, but was also significant in sculpture, poetry, theatre and painting. Notable painters include Santiago Rusiñol, Ramon Casas, Isidre Nonell, Hermen Anglada Camarasa, Joaquim Mir, Eliseu Meifrèn, Lluïsa Vidal and Miquel Utrillo. Notable sculptors are Josep Llimona, Eusebi Arnau and Miquel Blay.