"N.I.B." is a song released by British heavy metal band Black Sabbath. It first appeared as the fourth track on the band's 1970 self-titled debut album, Black Sabbath. The lyrics are in the first person from the point of view of Lucifer. Some listeners have claimed that the song is about Lucifer seducing the listener, however lyricist Geezer Butler clarifies that "The song was about the devil falling in love and totally changing becoming a good person." (quote from the 1992 documentary "The Black Sabbath Story: Volume One")

"N.I.B." begins with a bass solo by Geezer Butler, titled "Bassically" on some US releases. It involves the use of wah-wah on his bass and was recorded in one take, as the amp's volume control is plainly turned up before the distorted bass intro of 'N.I.B.' begins.

The title was widely rumoured to have stood for "Nativity in Black" (or to a much lesser extent, "Name In Blood"). In a 1992 interview, Geezer Butler states that the title simply refers to Bill Ward's goatee at the time, which the rest of the band thought was shaped like a pen nib.blank">http://www.black-sabbath.com/faq/faq11.htm#faq11040. "Nativity in Black" was also used for the title of a series of _Black Sabbath tribute albums. Ronnie James Dio can be heard mentioning (but not confirming) this assumption on several live bootleg recordings with the band from the early 1980s.

Many bands have covered the song, including Cave In, Type O Negative, Ugly Kid Joe, Acid Drinkers and Pitchshifter. Ozzy Osbourne and Primus recorded the song for Nativity in Black II. This version also appears in Osbourne's boxed set Prince of Darkness. The main riff is also played at the start of "Strange Ways" by Megadeth.

Additionally, the song appears in the music video game Rock Band as downloadable content in a 3-song pack, along with other Black Sabbath songs "Sweet Leaf" and "War Pigs."