Sigrún Hjálmtýsdóttir (pronounced [ˈsɪɣrun ˈçaulmtʰi(ː)sˌtouhtɪr]) (born 8 August 1955), better known as Diddú (pronounced [ˈtɪtːu]), is an Icelandic soprano and songwriter. Educated at the Reykjavík College of Music and the Guildhall School of Music and Drama in London, she began her singing career in the 1970s as a vocalist for the popular folk and pop group Spilverk Þjóðanna. She subsequently turned to classical music, particularly Lieder and operas.
Diddú's most recent album, Hvert Örstutt Spor (Each Tiny Step), was released in 2005.
The second of seven children of Hjálmtýr E. Hjálmtýsson, a bank clerk, and Margrét Matthíasdóttir, a writer, Diddú was born on 8 August 1955 and raised in Reykjavík. She studied at the Reykjavík College of Music, and afterwards at the Guildhall School of Music and Drama in London where she received a degree (1979–1984) and a postgraduate diploma (1985). She also had private singing lessons in Italy between 1987 and 1988.
Diddú began her singing career as a vocalist with the folk and pop group Spilverk Þjóðanna between 1975 and 1978 and made numerous recordings of folk and popular music, before turning her focus to classical music, particularly Lieder and operas. With the Icelandic Opera she has performed the parts of Susanna in The Marriage of Figaro, Gilda in Rigoletto, Papagena and the Queen of the Night in The Magic Flute, Lucia in Lucia di Lammermoor, Violetta in La traviata, Adina in L'elisir d'amore and Rosalinda in Die Fledermaus. She was a guest singer as Susanna in The Marriage of Figaro in Trondheim, Norway, and as Gilda in Rigoletto in Gothenburg, Sweden (1992). She has also sung the role of Olympia in Les contes d'Hoffmann (The Tales of Hoffmann) at the Þjóðleikhúsið (Thjodleikhusid, or National Theatre of Iceland) in Reykjavík.