Floor Jansen

Jansen was sixteen when she joined Apocalypse (later known as After Forever) in 1997. Three years later the band released its first album, Prison of Desire. Her ability to sing both classical and rock music has made her reasonably popular in the metal scene. She took sole charge of After Forever's lyrics and vocal melodies since the departure of Mark Jansen (no relation) in 2002. Prior to this, up until the Decipher (2001) album, the two would write together. Before becoming a full-time musician, she worked as a singing teacher.

Jansen started studying music at the Dutch Rock Academy in 1999, entering the Conservatorium Tilburg three years later. She studied musical theatre and a year of opera. After After Forever split up she started teaching performing in her own course called Wanna be a Star?!

Because of the burnout that After Forever bandmate Sander Gommans underwent, the band took a year off starting in January 2008 but ultimately decided to call it quits in February 2009. Jansen posted on her website, that while After Forever was on hold (and since then disbanded), she would use this opportunity to start writing music with Jørn Viggo Lofstad (Pagan's Mind, Jørn Lande) for a new musical project; the two would not be able to make the project come to fruition at the time due to their respective busy schedules, but would eventually reunite in 2017 to give birth to the project as Northward. On 16 June 2009, Jansen announced through her MySpace site, that she had started a new metal band, which has put the project called Sinh with Lofstad on hold.

On 17 October 2009, Jansen announced via MySpace, that the name of her new band was ReVamp. ReVamp's first album was produced with After Forever keyboardist Joost van den Broek, bass player Jaap Melman (formerly of Dreadlock Pussy) and guitarist Waldemar Sorychta (Grip Inc., Voodoocult, Eyes of Eden and Despair) as songwriters and producers. The final line-up of ReVamp featured keyboardist Ruben Wijga, bass player Jaap Melman, guitarists Jord Otto and Arjan Rijnen and drummer Matthias Landes.

In August 2011, Van Canto announced on Facebook, that ReVamp would no longer participate in their Out of the Dark tour, as Jansen suffered a burnout herself.

In late 2011, Jansen joined her former bandmate in After Forever Mark Jansen for his band MaYan's Latin American tour, performing in São Paulo. In 2012, Jansen joined Adrenaline Mob on stage in Bochum and Weert. ReVamp's second album, Wild Card, was released in 2013.

After Nightwish's previous lead vocalist Anette Olzon parted ways with the band, Jansen acted as Nightwish's live lead vocalist for the remainder of the Imaginaerum World Tour in 2012. She was at her sister's wedding when she received the call to replace Olzon. Her first show with the band was in Seattle in October. When commenting on the experience, she said:

On 9 October 2013, Jansen was announced as Olzon's permanent replacement in the band, following an invitation she received from the band in a hotel bar. In 2015, Nightwish released their first studio album featuring Jansen as the lead vocalist, Endless Forms Most Beautiful. Out of this tour came the live album Vehicle of Spirit which is the second live album to feature Floor.

On 9 December 2013, she was also announced as the main vocalist, playing the lead role, for the second full-length album of former Stratovarius guitarist Timo Tolkki's metal opera act Avalon. The album, Angels of the Apocalypse, was released on 16 May 2014. She has also been a guest for the metal band Nightmare.

ReVamp announced its breakup in September 2016, citing Floor Jansen's inability to deliver 100% to both ReVamp and Nightwish.

On 18 September 2016, it was announced, that Jansen and her husband Hannes Van Dahl, drummer of Sabaton, were expecting their first child. On 15 March 2017, Jansen announced via Instagram that she gave birth to a baby girl, Freja.

Three albums by the Dutch composer and multi-instrumentalist Arjen Anthony Lucassen's project Ayreon include guest vocals from Jansen: she sang backing vocals on "My House on Mars" from the album Universal Migrator Part 1: The Dream Sequencer, played the character of Forever (referred to as Ω) on seven songs from the album 01011001, and was featured as a character named The Biologist on the album The Source. She is also a member of Lucassen's heavy metal supergroup Star One, and was featured on the studio albums Space Metal and Victims of the Modern Age. She was also featured in the 2018 live album Ayreon Universe – The Best of Ayreon Live.

On 22 February 2018, Northward, a hard rock project by Jansen and Pagan's Mind guitarist Jørn Viggo Lofstad, was unveiled. The two created the project in 2007, writing an entire album worth of music in 2008 but being unable to record previously due to their busy schedules; they ultimately reunited in 2017 to finally record the album, which was released on 19 October 2018 under their signed label Nuclear Blast. The album features a duet between Jansen and her sister Irene.

In 2018, a new species of beetle was discovered by scientist Andreas Weigel. It was named after Jansen, dubbing it Tmesisternus floorjansenae. This makes Floor Jansen the second Nightwish member to be a namesake for a newly discovered species, as a new kind of fungus gnat was discovered back in 2017 by Finnish biologist Jukka Salmela, who named the species after Tuomas Holopainen. Jansen herself announced the news on Facebook.

In 2019, Jansen participated in the Dutch TV-show Beste Zangers ("Best Singers"). During all episodes she impressed her fellow singers, but also the TV-audience with her voice. In the last episode she partnered with classical singer Henk Poort to perform Phantom of the Opera. The single of that performance reached the number one position in Dutch charts. That performance generated so much attention that she decided to plan a solo tour in the Netherlands. All venues were sold out. She also won the "Popprijs 2019" - a prestigious Dutch award for the artist or band with an important contribution to Dutch pop music in the past year.

The second studio album with Jansen as lead vocalist, Human. :II: Nature., was released on April 10, 2020.