Declan Michael Martin Donnellan OBE (born 4 August 1953) is an English film/stage director and author. He co-founded the Cheek by Jowl theatre company with Nick Ormerod in 1981. In addition to his Cheek by Jowl productions, Donnellan has made theatre, opera and ballet with a variety of companies across the world. In 1992, he received an honorary degree from the University of Warwick and in 2004 he was made a Chevalier de l'Ordre des Arts et des Lettres for his work in France. In 2010, he was made an honorary fellow of Goldsmiths' College, University of London. Donnellan was appointed Officer of the Order of the British Empire (OBE) in the 2017 Birthday Honours for services to theatre.

Donnellan was born in Manchester and grew up in Ealing, London. He was educated at St Benedict's School, Ealing and Queens' College, Cambridge, where he read English and Law. After leaving Cambridge, he was called to the Bar at Middle Temple in 1978.

He founded Cheek by Jowl with Nick Ormerod in 1981. Since 2006 the company has been part of the Barbican's International Theatre Program (BITE) resulting in co-productions of The Changeling (2006), Cymbeline (2007) and Troilus and Cressida (2008). He has directed plays at the Royal Shakespeare Company, the English National Opera, the Old Vic and the Bolshoi Ballet, among others.

For the Royal Shakespeare Company he has directed The School for Scandal, King Lear (Academy 2002) and an adaptation of Great Expectations (2005) with Nick Ormerod. The cast of Great Expectations included Gwendoline Christie and Sian Phillips. He has also directed Le Cid for the Avignon Festival, Falstaff for the Salzburg Festival and the ballet of Romeo and Juliet for the Bolshoi Theatre in Moscow. Other work in Russia includes The Winter's Tale for the Maly Drama Theatre of Saint Petersburg.

In 1989, Donnellan was made Associate Director of the Royal National Theatre in London where his productions have included Fuenteovejuna, The Mandate and Sweeney Todd: The Demon Barber of Fleet Street (1993) The cast of Sweeny Todd included Alun Armstrong, Adrian Lester and Julia McKenzie. In 1993 Donnellan directed both parts of Angels in America, after having previously directed the play’s first part Millennium Approaches at the National’s Cottesloe Theatre in 1991. In 1993 the play’s second part, Perestroika, received its London debut at the National Theatre and was played in repertory with Millennium Approaches, starring Daniel Craig and Jason Isaacs.

In 2000 he formed a company of actors in Moscow, under the auspices of The Chekhov Festival, whose productions include Boris Godunov, Twelfth Night and Three Sisters. He wrote a play, Lady Betty, which was performed by Cheek by Jowl in 1989. He has also adapted Don't Fool with Love by Alfred de Musset, Antigone by Sophocles, The Mandate by Nikolai Erdman and Masquerade by Mikhail Lermontov. First published in Russian in 2001, Donnellan's book, The Actor and the Target, was published in English in 2002 (reprinted 2005), and has since appeared in 15 languages, including French, Spanish, Italian, German, Romanian and Mandarin.

He directed the 1992 short The Big Fish which starred Fiona Shaw. He directed the 2012 film Bel Ami, an adaption of the Maupassant novel; the film starred Robert Patinson, Uma Thurman, Kristin Scott Thomas, Christina Ricci and Colm Meaney.

Donnellan has won awards in London, Paris, New York and Moscow, including Laurence Olivier Awards for: