Claes-Håkan Ahnsjö (born 1 August 1942) is a Swedish operatic tenor particularly associated with the baroque repertoire and Mozart works.
He made his debut at the Royal Swedish Opera in 1969, as Tamino in The Magic Flute, later singing Belmonte, Idamante, Don Ottavio and Ferrando.
From 1969, he also became a regular at the summer opera festival at Drottningholm Palace Theatre, which focused on works by Handel, Gluck, Haydn, and Mozart.
In 1973, he joined the Bavarian State Opera in Munich, where he sang a large number of lyric roles including Armand des Grieux in Boulevard Solitude, Almaviva in Il barbiere di Siviglia, Nemorino in L'elisir d'amore, Ernesto in Don Pasquale, Duke of Mantua in Rigoletto, Alfredo in La traviata, Fenton in Falstaff, Des Grieux in Manon, Nicias in Thaïs, David in Die Meistersinger von Nürnberg and the title role in Britten's Albert Herring.
In 1991, he played the role of Agenore in a live staging of Mozart's Il re pastore, alongside Sylvia McNair, Jerry Hadley and Iris Vermillion, with Neville Marriner conducting the Academy of St Martin in the Fields.