Daniel O'Sullivan is a British musician and composer from Manchester, best known for playing in experimental art-rock bands Grumbling Fur, Guapo, Miasma & the Carousel of Headless Horses, Ulver, Sunn O))), Æthenor, Laniakea, Miracle, Mothlite, and This Is Not This Heat. He's also released solo work under his own name.

Terrestrials is a collaborative studio album by American drone metal band Sunn O))) and Norwegian experimental music group Ulver. Produced by Stephen O'Malley and Kristoffer Rygg, it was released on February 3, 2014, via Southern Lord Records. It has been described as "three live improvisation pieces".