O’Malley was born in New Hampshire, USA and raised in Seattle. After forming Sunn O))) with Greg Anderson in 1998, he also founded the groups Khanate (2000), KTL (2005), Nazoranai (2011), and ÄÄNIPÄÄ (2011). He left Seattle for New York, where he spent ten years, and is now based in Paris. He collaborates frequently with outsider musicians, artists, and composers in various formations and in both live and studio settings. He helped create the record labels Southern Lord (in 1998) and Ajna Offensive (in 1995) and worked as the art director for Misanthropy Records from 1997 to 2000. In 2011 he created Ideologic Organ, an Editions Mego sublabel, together with Peter Rehberg.

O’Malley’s work is defined by its remarkable breadth and variety and has been marked by joint efforts with a wide range of experimental musicians, including Scott Walker, Merzbow, Jim O’Rourke, Keiji Haino, Mats Gustaffson, Peter Rehberg, and Oren Ambarchi; French choreographer and theater director Gisèle Vienne; author Dennis Cooper; Israeli conductor Ilan Volkov; American sculptor Banks Violette; Italian performance artist Nico Vascellari; American filmmaker Jim Jarmusch; Fashion designer Rick Owens; Belgian filmmaker Alexis Destoop; and contemporary composers Roger Tessier, Eyvind Kang and Alvin Lucier, and Iancu Dumitrescu, with whom he will appear at CTM 2016.