Apostolos Doxiadis (/dɒksiˈædɪs/; Greek: Απόστολος Δοξιάδης [ðoksiˈaðis]; born 1953) is a Greek writer. He is best known for his international bestsellers Uncle Petros and Goldbach's Conjecture (2000) and Logicomix (2009). Most of Doxiadis’ writing in recent decades has been fiction and essays, but he has also written for the theatre and composed librettos for musicals. In the past, he had also worked as a director in theatre and film.

Doxiadis was born in Australia, where his father, the architect Constantinos Apostolou Doxiadis was working. Soon after his birth, the family returned to Athens in Greece, where Doxiadis grew up. Though his earliest interests were in poetry, fiction and the theatre, an intense interest in mathematics led Doxiadis to leave school at age fifteen, to attend Columbia University, in New York, from which he obtained a bachelor's degree in mathematics. He then attended the École Pratique des Hautes Études in Paris from which he got a master's degree, with a thesis on the mathematical modelling of the nervous system. Before his father's death from ALS in 1975, the resulting family needs made him return to Greece, interrupting his graduate studies. Soon after addressing the needs, Doxiadis gave all his time to his artistic work.

In 1998, Doxiadis translated into English, significantly re-working, his third novel, which was published in England in 2000 as Uncle Petros and Goldbach's Conjecture (UK publisher: Faber and Faber; United States publisher: Bloomsbury USA.) The book became an international bestseller, and has been published to date in more than thirty-five languages. It has received the praise of, among others, Nobel laureate John Nash, British mathematician Sir Michael Atiyah, critic George Steiner and neurologist Oliver Sacks. Uncle Petros is one of the 1001 Books You Must Read Before You Die.

Doxiadis' next project, which took over five years to complete, was the graphic novel Logicomix (2009), a number one bestseller on the New York Times Best Seller list and an international bestseller, already published in over twenty languages. Logicomix was co-authored with computer scientist Christos Papadimitriou, with art work by Alecos Papadatos (pencils) and Annie Di Donna (colour). Renowned comics historian and critic R. C. Harvey, in the Comics Journal, called Logicomix "a tour-de-force" a "virtuoso performance", while The Sunday Times' Bryan Appleyard called it "probably the best and certainly the most extraordinary graphic novel" he has read. Logicomix is one of Paul Gravett's 1001 Comics You Must Read Before you Die.

Doxiadis began to write in Greek. His first published work was A Parallel Life (Βίος Παράλληλος, 1985), a novella set in the monastic communities of 4th-century CE Egypt, dealing with the conflict between faith and temptation. His first novel, Makavettas (Μακαβέττας, 1988), recounted the adventures of a fictional power-hungry colonel at the time of the Greek military junta of 1967–1974. Written in a tongue-in-cheek imitation of Greek folk military memoirs, such as that of Yannis Makriyannis, it follows the plot of Shakespeare's Macbeth, of which the eponymous hero's name is a Hellenized form. Doxiadis next novel, Uncle Petros and Goldbach's Conjecture (Ο Θείος Πέτρος και η Εικασία του Γκόλντμπαχ, 1992), was the first long work of fiction whose plot takes place in the world of pure mathematics research. The novella The Three Little Men (Τα Τρία Ανθρωπάκια, 1998) was later expanded into the longer novel The Three Little Pigs, which reworks motifs from the "Three Little Pigs" fairy tale in a crime narrative, a morality tale set in the world of the Italian Mafia. The novel has appeared in translation, including Spanish as Tres cerditos (Alianza Editorial, 2017), Italian as Tre piccoli porcellini: tre fratelli, un gangster, una maledizione (Bompiani), and German as Des Menschen Wolf (Tropen, 2017).

Doxiadis's upcoming novel, Bluedog (Γαλανόσκυλος), is scheduled for publication on 19 March 2026. Blending realistic and fantastic elements, the narrative alternates between 1990s Greece and the 1940s during the Axis occupation. Thematically, it explores the contrast between modernity and tradition.

In Amateur revolutionary (Ερασιτέχνης επαναστάτης, 2018), an autobiographical narrative described as a "personal myth-history", Doxiadis recounts his life from childhood to early adulthood, focusing on his political formation during the years of the Greek military dictatorship.

He followed his first direct memoir with a work of autofiction, The phone call that never was (Το τηλεφώνημα που δεν έγινε, 2022). The narrative is centered on his first artistic work in his adolescence and the conflict with his father it led to, framed by a contemporary, partly fictional inquiry into the meaning of that work.