Sinfóníuhljómsveit Íslands (Iceland Symphony Orchestra) (ISO) is an Icelandic orchestra based in Reykjavík. The ISO is an autonomous public institution under the auspices of the Icelandic Ministry of Education. The Iceland Symphony Orchestra made its home in Háskólabíó (University Cinema) from 1961–2011, but moved into the new 1800-seat Harpa (Reykjavík Concert and Conference Center) in spring 2011. The orchestra gives approximately sixty concerts each season. Per a 1982 law, the ISO's primary financial sources are the Icelandic treasury (56%), RÚV (Icelandic National Broadcasting Service) (25%), and the City of Reykjavik (18%), with the remaining 1% coming from the township of Seltjarnarnes.

Around 1925, a small orchestra of about 15 players, the Hljómsveit Reykjavíkur (Reykjavík City Orchestra), began to give concerts. Further institutional roots of the orchestra came with the foundation in 1930 of the RÚV and of the Reykjavík College of Music. The RÚV had a radio orchestra for several years. The ISO was formally founded in 1950, giving its first concert on 9 March 1950, with an ensemble of 39 players.