Black One is the fifth studio album by American drone metal band Sunn O))). As the title implies, the album is very black metal-influenced; utilizing many guest musicians of the genre including Malefic and Wrest from Xasthur and Leviathan respectively. Allegedly Malefic, a sufferer of claustrophobia, was locked in a casket during his recorded performance to the vocals on the track "Báthory Erzsébet".

2,000 copies included a bonus disc titled Solstitium Fulminate, containing a mix of live performances recorded at Roskilde Festival in 2005 and the immediately preceding European tour.

"Orthodox Caveman", previously known as "Caveman Salad", is based on live material from the White (see Live White) tour. "Báthory Erzsébet" was recorded as a tribute to Quorthon (as well as the countess who inspired Bathory's name) and, according to an interview with Terrorizer magazine, is loosely built "around a really slowed down riff from 'A Fine Day to Die'".