Nightwish is a Finnish symphonic metal band from Kitee. The band was formed in 1996 by lead songwriter and keyboardist Tuomas Holopainen, guitarist Emppu Vuorinen, and former lead singer Tarja Turunen. The band soon picked up drummer Jukka Nevalainen, and then bassist Sami Vänskä after the release of their debut album, Angels Fall First (1997). In 2001, Vänskä was replaced by Marko Hietala, who also took over the male vocalist role previously filled by Holopainen or guest singers. Although Nightwish have been prominent in their home country since Angels Fall First, they did not achieve wider success until the release of the albums Oceanborn (1998), Wishmaster (2000) and Century Child (2002).

Their 2004 album, Once, has sold more than one million copies and was the band's breakthrough in the United States. Their biggest US hit single, "Wish I Had an Angel" (2004), received MTV airplay and was included on three US film soundtracks. The band produced three more singles and two music videos for Once, as well as a re-recording of "Sleeping Sun" for the compilation album, Highest Hopes: The Best of Nightwish (2005), before Turunen's dismissal in October 2005. In May 2007, Nightwish announced Anette Olzon as Turunen's replacement. That September, the band released their sixth album, Dark Passion Play, which has sold almost 2 million copies. The album's lead single, "Amaranth", became one of Nightwish's most successful in Europe. Their seventh studio album, Imaginaerum, was released in November 2011. Nightwish parted ways with Olzon in October 2012 and finished the tour with Floor Jansen, who later became a permanent member of the band alongside longtime session uilleann pipes player Troy Donockley in October 2013.

In July 2019, Nevalainen who had been inactive since 2014 due to severe insomnia issues, announced that he would not be returning to the band, with Kai Hahto, who had acted as his replacement since 2014, being promoted as the official drummer. After twenty years of performing with the band, bassist Marko Hietala had parted ways with the band in January 2021, and Jukka Koskinen was later announced as Hietala's replacement in August 2022.

Nightwish is the third-best-selling band and musical entity in Finland with certified sales of nearly 900,000 certified copies. The group is also the most successful Finnish band worldwide, selling more than 10 million records and receiving more than 60 gold and platinum awards, having released six Number 1 albums and thirteen Number 1 singles. On October 26, 2018, Nightwish was inducted into the Finnish Music Hall of Fame, becoming the honorary gallery's 11th member.