Costas Taktsis (Greek: Κώστας Ταχτσής, 8 October 1927 – 25 August 1988) was a Greek writer. Described as a "landmark of post-war literature in Greece", Taktsis wrote The Third Wedding (Greek: Το τρίτο στεφάνι, romanized: To tríto stefáni) partly in Australia. The book unfolds in the years before and after World War II through the flowing personal narrative of two women: Ekavi and Nina, who speak in a direct and everyday language about what they live through. Unable to find a publisher in Greece he published it at his own expense in 1962. The book has been translated into 18 languages. The French edition was released by Éditions Gallimard in 1967, translated by Jacques Lacarrière. In 1969 it became the first Greek novel published by Penguin Books. A new English translation by John Chioles, was published as The Third Wedding Wreath, by Hermes in 1985.

Many directors including Michael Cacoyannis unsuccessfully tried to produce a film based on the book. Greek broadcaster ANT1 TV produced a television series based on the book in 1995 with Nena Menti in the role of Nina and Lida Protopsalti as Ekavi. A 4-hour adaption for the theatre, directed by Stamatis Fassoulis was produced by the National Theatre of Greece in 2009–2010.

Multi-lingual, he also translated ancient Greek drama, mainly Aristophanes' comedies (The Frogs, The Clouds, The Birds (play), Lysistrata), as well as foreign literature. Together with Nanos Valaoritis and others he participated in the editorial team of the pioneering literary magazine Pali (1964–1967). One theme that is ubiquitous in Taktsis's later texts is homosexuality, which he sometimes accepts and sometimes sees as a permanent curse.