Mark O'Leary was born in Cork City Ireland.Being mainly auto didactic on guitar he moved to Los Angeles at the age of 17 to study at Musicians Institute,from where he later graduated. He has presented his music in 29 countries and has played at some of the worlds top Jazz festivals and contemporary Jazz venues.
He has toured Europe as a member of Canadian Pianist Paul Bley's trio,he has performed in duo with Jack DeJohnette,in a jazz trio with Yes/King Crimson drummer Bill Bruford, in duo with Han Bennink,composed and performed classical music with Cikada string quartet,collaborated in an all electronics setting with Sound Artist Gunter Muller, Erdem Helveciouglu and Jakob Riis,in a free improvisation combo with Evan Parker and Sunny Murray, performed in concerts with Anders Jormin and Audun Kleive, played Norwegian folk music with Nils Okland, Swedish folk music with Mats Eden, Jazz with Uri Caine, he has performed in seperate projects with trumpeters Axel Dorner,Kenny Wheeler, Thomas Heberer and Jeff Kaiser. He has the distinction of having played in duo with Paul Bley, Bobo Stenson and Matthew Shipp. In 2004 he toured Serbia, Bosnia and Montenegro with Vasil Hadzimanov and Marco Djordevic. He also toured in Macedonia with Guitarist Toni Kitanovski and Drummer Alexander Sekhulovski. He also represented Ireland in the Athens European jazz festival.
He has also worked in a trio with ex Weather Report/Jaco Pastorius Drummer Peter Erskine and Palle Danielsson. He has also collaborated with the innovative percussionists z'ev, Alex Cline ,Hans Kristian Kjos Sorensen and Terje Isungset.He has also collaborated with Stale Storlokken in contemporary trio using church organ and with John Herndon of Tortoise in the Underground Jazz Trio.