Kaija Saariaho (Finnish: [ˈkɑi̯jɑ ˈsɑːriɑho]; née Laakkonen, born 14 October 1952) is a Finnish composer.

Kaija Saariaho studied composition in Helsinki, Freiburg and Paris, where she has lived since 1982. Her studies and research at IRCAM have had a major influence on her music and her characteristically luxuriant and mysterious textures are often created by combining live music and electronics. Although much of her catalogue comprises chamber works, from the mid-nineties she has turned increasingly to larger forces and broader structures, such as the opera L’amour de loin, premiered at the 2000 Salzburg Festival (with a US premiere at the Santa Fe Opera in 2002), and Oltra mar for chorus and orchestra, commissioned by the New York Philharmonic. Her second opera, Adriana Mater, was commissioned for the Opéra National de Paris’ 2006 season. Her second string quartet, Terra Memoria, was commissioned for the Emerson Quartet by Carnegie Hall for a June 2007 premiere. The third opera, Émilie, has the life and death of Émilie du Châtelet as its topic. The librettist of all of the three operas is Amin Maalouf.