The idea of Nightwish was "born" in July 1996 at midnight when Tuomas was spending a night with his friends around a campfire. The first three songs, which were acoustic mood music, were recorded between October and December 1996. At that time, the band had three members: Tuomas, Tarja and Emppu.

The band wanted to see what the music would sound like if drums were added (Jukka joined the band). Also at this time, the acoustic guitar was replaced with an electric. After a couple of weeks of training, the band went to the studio this was in April 1997. At that time seven songs were recorded. These songs can be found on the limited edition of the album Angels Fall First. In May 1997, Nightwish signed a recording contract with Spinefarm for two records. That August, the band went to the studio and recorded four new songs. Before the release of Angels Fall First, a single called The Carpenter was released, and made it to number eight on the official singles chart in Finland. Angels Fall First was released in early November and went number 31 on the official album chart in Finland. Nightwish played their first gig in Kitee on the 31st December 1997. After that Nightwish played only seven gigs in the following winter because Jukka and Emppu were in the army and Tarja was busy with her studies. Nightwish and at this time, Spinefarm extended the contract to include three records instead of two.

In April 1998, they started filming the first video, The Carpenter. It was ready in early May and was first played on Jyrki. In late May, Tuomas and Tarja interviewed on that show. In the following summer, the bassist Sami Vänskä joined the band. During the summer, songs for the new record were rehearsed and the band went to the studio in early August; the recordings were finished in late October. On November 13th, Nightwish played a gig in Kitee during which, a video for Sacrament of Wilderness was filmed. That song's single was released on November 26th and the new record called Oceanborn was released on December 7th. Everybody was surprised by the success of Oceanborn. It went up to fifth place on the official Finnish album chart and the single Sacrament of Wilderness was the number one on the singles chart for weeks.

In winter 1999, Nightwish played a lot of gigs all around the country for three months which included a gig on the Lista chart show program. In spring Oceanborn was first released outside of Finland. In May, the band started to play gigs again and toured the country for two and a half months, playing in almost all of the big rock festivals. At the same time the single Sleeping Sun was recorded, which was written for the eclipse in Germany. In August, the single was released in Germany and it also included the songs Walking in the Air, Swanheart, and Angels Fall First. In Germany alone the single sold 15,000 copies in just one month. In August, Nightwish learned that Oceanborn and Sacrament of Wilderness had sold gold. At the same time it was confirmed that Nightwish would be touring Europe for 26 gigs with the German band Rage.

In early 2000 the band entered the studio again for the recording of their third album. A welcome interruption came to the repetitive studio work when they took part in the Finnish qualification for the Eurovision Song Contest with the song Sleepwalker. Nightwish cleared the first round of the qualification, but the final position was second despite an overwhelming win in the public televoting. The new album, Wishmaster, was released in May and the Wishmaster Tour started from Kitee, the home town of the band. After the show, the band received gold discs for the album Oceanborn and the singles Sacrament of Wilderness, Walking in the Air, and Sleeping Sun. Wishmaster went straight to number 1 on the Finnish album charts and stayed in that position for three weeks, during that time, it also reached the gold disc mark. Wishmaster was approved by both the fans and the media and it was named the album of the month by the German magazine Rock Hard in their issue 6/2000, past the long-awaited new releases by Bon Jovi and Iron Maiden. Wishmaster also debuted in the National German Charts at No. 21 and No. 66 in France! The "Wishmaster World Tour", which started from Kitee, continued first to the big festivals in Finland and then to South America in July 2000. The three-week tour in Brazil, Chile, Argentina, Panama and Mexico turned out to be one of the band's greatest experiences so far. This was followed by successful shows at Wacken Open Air, Biebop Metal Fest and the first headliner European tour with Sinergy and Eternal Tears Of Sorrow. In November, Nightwish also played two shows in Montreal, Canada. The next project of Nightwish included the making of a full-length concert DVD & VHS with a limited live album (only for Finland). The concert was performed in Tampere on the 29th of December 2000. The material was released in April 2001 in Finland and worldwide during the summer of 2001. At the end of the show, Nightwish were given platinum discs for "Wishmaster" and gold discs for the single "Deep Silent Complete".

In March 2001 Nightwish entered the studio again to record their version of Gary Moore's classic Over The Hills And Far Away, with 2 new songs and a remake of Angels Fall First's "Astral Romance". The Finnish release for this EP was in June 2001. The German version of "Over The Hills And Far Away" (released by Drakkar) includes 6 live tracks in addition to the 4 unreleased songs. Nightwish has also extended the record deal with Spinefarm Records with one full-length album, which was set to be released in Summer 2002. The video for the track "Over the Hills and Far Away", which had rapidly sold platinum in Finland as a mini-CD, was shot in August 2001 in Finland. The tour in Finland the same year ended in Nivala, and the band was close to disbanding. Tuomas went hiking and gathering his thoughts in Lappland; some changes had to be done in order for Nightwish to be able to continue. According to his own words, Tuomas wanted to end the band due to prolonged disagreements within the band. Luckily, that didn't happen. But something happened, a lot in fact. Sami Vänskä, who had been with them since Oceanborn, had to leave. Marco Hietala, known from Tarot and Sinergy, promised to step in as a replacement for the next album and tour. King Foo Entertainment became their new booking agency, and long-time friend and colleague, Ewo Rytkönen, was to become their manager. To celebrate the "new beginning", the first official shop for fan-products, Nightwish-Shop, was opened on the band's homepage on November 24th 2001, a month before Christmas. The recording of the next album Century Child started in January 2002.

The beginning of 2002 brought Nightwish good news, in comparison to previous rough times. As a band and as individual musicians they were voted to the top on many domestic and foreign magazines reader's polls. The fans had not abandoned them after the changes, on the contrary. Ever Dream, the first single from the forthcoming album, went gold in Finland within 2 days. At the same time Nightwish announced they would take a break as soon as the "Century Child World Tour 2002" would be over, Tarja would finish her educations in Germany during the break. That announcement brought up all kinds of speculations among fans. Sami leaving the previous Fall, now a break that would last a year... Century Child came out in May 2002 and made a sales record, selling gold in Finland within 2 hours! Within two weeks it sold platinum (30,000 copies) and continued selling rapidly. At the same time Nightwish held the top-position in both singles-and album charts, for their first time ever. Foreign countries responded, too: in Germany, Century Child went straight to number 5 and in Austria, number 15, those two being the band's highest positions abroad so far. In July, Nightwish toured successfully in South America, where nearly all gigs sold out. In Brazil, the first edition of Century Child was sold out in one day, and the successful European tour that year didn't go unnoticed by booking agencies. Many European gigs were broadcasted live on the internet, needless to say the connections were often jammed. At its most, nearly 10,000 fans were trying to follow the live feed. Having sold an astonishing 59,000 copies in Finland, Century Child was the country's 2nd best selling album in 2002. The first visit to Sweden took place on 16th November 2002, in Fryshuset, Stockholm. The break started in late 2002, and sure enough there was no rest for the guys. Jukka played with Sethian and Bitch Driven, Tuomas with Sethian, For My Pain..., and Timo Rautiainen & Trio Niskalaukaus, Emppu played with Altaria, and Marco with Tarot. All in all the break wasn't to last nearly a year, back on the road...

The beginning of 2003 saw more good results in reader's polls of various magazines, and a studio was booked in order to start recording the next album, planned to be released the next year. Happenings also at the home-front: Jukka and his girlfriend Satu had a daughter, Luna, on March 11, 2003. Nightwish received their first double-platinum award for Century Child, having sold 60,000. The band performed mostly abroad in 2003, the only gig in Finland was at RMJ 2003 on June 20th. The second visit to Sweden took place at the sold out "Gates of Metal"-festival in Hultsfred. During 2003, the forthcoming DVD-documentary End of Innocence was being put together, and it's release was postponed a few times due to huge amount of material. In May 2003, Tarja Turunen announced that she had secretly gotten married a few months earlier, and would be moving back to Finland. The DVD "End of Innocence" was finally released on October 6th 2003, and at that point, Nightwish had already started recording the next album. Their fifth album "Once" would be the most important release in the history of Nightwish. Meanwhile, Finland's President, Tarja Halonen, had also taken note of Nightwish's achievements and invited Tarja Turunen and her husband Marcelo Cabuli to the annual independence-day party held at the presidential residence. Tarja's dress was voted as the most beautiful dress that evening. Before the Christmas of 2003 Nightwish auctioned their "Century Child World Tour"-backdrop, and donated all the money to charity. The outcome was 1,750 EUR, and was given to Parikanniemi's Children's home in Ristiina on December 2003. The funds were handed out by Tarja Turunen, Michael "Big Tini" Leipold from Germany became the new proud owner of the backdrop.

The year 2004 was eagerly expected by both the fans and the band. Exhausting studio-sessions took their toll both physically and mentally. The actual recording took place at the Phoenix-studios in London, the same studio and with the same orchestra (The Academy of St. Martins in the Field) that Howard Shore used for writing the score for "The Lord of the Rings"-trilogy. Orchestral-and choral arrangements were written by Pip Williams, who has produced "Status Quo"and "riah Heep" Big time, great expectations! Nemo was the first single released off the forthcoming album, and a big-budget video was made. The director was Antti Jokinen, who had previously worked with Shania Twain and Eminem. With the new album, Nightwish had some changes with the recording contract, and the new material was released by Nuclear Blast. Good old Spinefarm Records would still handle the distribution in Finland. Nuclear Blast spent a considerable amount of money marketing Once, especially in Germany. Pictures of Nightwish and Once were splattered all over the television-channels, subways, buses and streets, and the press wasn't forgotten either. Every German will know Nightwish by now. Once went gold in Finland on its day of release, as did the single "Nemo". Nightwish started a world Tour of 150 concerts in all continents, the tour lasted until the end of 2005. This tour was be the biggest in the history of Nightwish so far. The album "Once" sold gold in Finland immediately on its release day, as did the single "Nemo". In May 2004, Nightwish started the Once World Tour. The Once World Tour lasted until the end of October 2005. There were about 130 gigs all over the world, including new countries such as Japan, Australia, Colombia, Ecuador, Poland, Slovenia, Portugal, Denmark, and Greece. The tour was the biggest in Nightwish's history. From month to month the venues grew bigger and the news told about success. The second single, Wish I Had An Angel, was released in Autumn 2004. The song's video was directed by Uwe Boll, director of the movie "Alone In The Dark", in which the song was also played. The second single was again a great success and boosted the sales of the Once album. In August, Nightwish finally made it to the USA! The tour was very successful and they planned to come back for a bigger tour in 2005. After the tours in Europe and South America in the Autumn of 2004, and some separate gigs in December, the band had some time off in January 2005.

In February 2005, Nightwish won five awards in Emma-Gala (Finnish Grammy). Among the others they won awards for "The Band of the Year" and "The Best Selling Album of the Year". Tuomas and Marco flew from European tour to Helsinki to receive the awards. The last show in the European tour was so far the biggest gig of their own, in Stuttgart there were 10,001 people watching the show! In March, Nightwish performed the first time in Japan and Australia; in April and May, they had to have a break because of Tarja's other interests, but at the end of May the band started the tour again by playing with Iron Maiden in Poland and with Mötley Crüe in Norway. In July, the 3rd single, a new version of Sleeping Sun, was released since the record label had decided to use it to promote the forthcoming collection Highest Hopes. The new version of the video for "Sleeping Sun" was directed by Joern Heitmann and shot in August 2005 in Prague. During the Autumn 2005, Nightwish played several shows and performed in the legendary Hammersmith Apollo Venue for sold out seats. After a short festival tour in South America (in October), the Once World Tour was coming to an end. The final concert was played on 21 October for 11,500 people in Hartwall-Arena in Helsinki. The concert was also recorded to be released as an End of an Era live DVD. After the last concert, Tuomas, Emppu, Marco and Jukka fired Tarja Turunen, and her manager Marcelo Cabuli. The reason for this was because during the Once Tour their attitude and actions had turned out to be against almost all that Nightwish represents. As one may guess, the news of the firing was followed by an incredible sensation and hullabaloo. Once the nearly ridiculous fuss was finally starting to calm down in the end of 2005, Nightwish was able to look to the future and wait for an adequate singer to be found. By the end of 2005, "Once" has sold approx. 1,000 000 copies worldwide as well, it has sold triple platinum in Finland, platinum in Germany, and gold in Sweden, Norway, Switzerland, Greece, and Austria. The "Highest Hopes" collection has sold double platinum in Finland and gold in Norway by the end of the year 2005.