In Spring 1999 during Edguy’s Theater Of Salvation tour, Tobias Sammet began to outline his ideas for a metal opera concept album featuring a number of guest musicians.
When the tour was finished, he began to join forces with metal vocalists Michael Kiske, Andre Matos, Kai Hansen, Rob Rock, David Defeis, Sharon den Adel, Bob Catley and Oliver Hartmann to record the project.
At this stage the core band consisted of four members, Tobias Sammet on keyboards, Henjo Richter on guitar, Markus Grosskopf on bass and Alex Holzwarth on drums.
In 2001, a self-titled single and the first full length album, The Metal Opera, was released.
The project went on after the release of The Metal Opera Part II in September 2002.
At the end of 2006, Tobias Sammet did the announcement of the third Avantasia album, which was release in 2008.
Two EP’s named Lost In Space Part I and Lost In Space Part II were released in November 2007, and the full length album, The Scarecrow, was released in January 2008.
The Scarecrow is the first chapter of The Wicked Trilogy concept, and was also the first of many Avantasia releases to feature Sascha Paeth in the role of main guitarist and producer. The album included guest performances by drummer Eric Singer, guitarists Henjo Richter and Rudolf Schenker and singers Jørn Lande, Michael Kiske, Bob Catley, Alice Cooper, Roy Khan, Amanda Somerville and Oliver Hartmann.
After the release of The Scarecrow, Tobias Sammet was invited to perform a headlining show at Wacken Open Air, an offer that producer and guitarist Sascha Paeth convinced him to accept.
That led to 13 shows between 5 July and 13 August. The shows at Masters Of Rock and Wacken Open Air were recorded and the live DVD The Flying Opera, based on the footage, was released in March 2011.
The line-up for the short tour consisted of Tobias Sammet, Andre Matos, Jørn Lande, Kai Hansen, Bob Catley, Amanda Somerville, Cloudy Yang, Sascha Paeth, Oliver Hartmann, Robert Hunecke, Miro and Felix Bohnke. 
In November 2009 Tobias Sammet announced that he was recording two new albums, The Wicked Symphony and Angel Of Babylon, to be released in April 2010.
The concept of the albums was a continuation of The Scarecrow story, and these three albums together are often referred to as The Wicked Trilogy.
The special guests included drummers Eric Singer, Alex Holzwarth and Felix Bohnke. Guitarists Bruce Kulick and Oliver Hartmann.
Keyboardist Jens Johansson and vocalists Jørn Lande, Russell Allen, Michael Kiske, Bob Catley, Klaus Meine, Tim Owens, Jon Oliva, Andre Matos, Cloudy Yang and Ralf Zdiarstek.
The Scarecrow, The Wicked Symphony and Angel Of Babylon have scored high positions in various international music charts.
In 2010 Avantasia played live in Stockholm.
In December 2010 a tour of 12 shows in Europe, South America and Asia took place, except for one concert at the Wacken Open Air festival in August 2011.
The shows lasted for almost three hours, and many of them were sold out days before.
The ensemble was almost the same as on The Scarecrow tour in 2008, with two changes. Andre Matos was replaced by Michael Kiske, and together with Kai Hansen participating on this tour there were a lot of instances when the two Helloween members shared the same stage and the fact that Cloudy Yang was not part of the line-up.
After the worldwide success of the studio releases, and an arena world tour that was sold out pretty much everywhere, collaborations with childhood heroes.
Tobias knew that he had said everything he could possibly say in the name of Avantasia.
But that’s not what Avantasia is all about.
He wanted to create more great music, he wanted to create more fantasy worlds, bigger and more epic, and better.
And listening to the material that he had created for this forth coming chapter in the history of Avantasia, Tobias know there is no way he is not going to do it.
And he has got the feeling, and the certainty, that this is absolutely meant to happen and to be.
In March 2013 The Mystery Of Time marked the beginning of a new concept.
The album included guest performances by drummer Russell Gilbrook, guitarists Bruce Kulick, Oliver Hartmann and Arjen Anthony Lucassen, while the guest vocalists were Joe Lynn Turner, Biff Byford, Michael Kiske, Ronnie Atkins, Eric Martin, Bob Catley and Cloudy Yang.
The Mystery Of Time scored high positions in several international music charts and even enabled the project to enter the US Billboard charts for the very first time.
Avantasia’s second-biggest world tour took place between April and August 2013.
The tour consisted of 30 concerts and included 7 headlining festival appearances in Europe, one festival performance in Canada and shows of 3 hours in South America, Japan, Russia, Germany, Switzerland, Italy, and The Netherlands.
The line-up for the tour consisted of vocalists Tobias Sammet, Michael Kiske, Ronnie Atkins, Eric Martin, Bob Catley, Thomas Rettke, Amanda Somerville and musicians Sascha Paeth, Oliver Hartmann, Miro, Andre Neygenfind and Felix Bohnke.
Tobias Sammet wanted to put on the biggest thing you have ever seen, wanted to bring more vocalists, play longer shows, and make it a big Rock Opera show.
Tobias Loves to headline festivals for 90 minutes and kick ass.
But he also liked to do his own Avantasia indoor tour because that way he can make it much more Avantasia oriented and play for almost 3 hours.
In January 2016 the album Ghostlights was released featured guest performances by guitarists Bruce Kulick and Oliver Hartmann, while the guest vocalists were Jorn Lande, Michael Kiske, Dee Snider, Geoff Tate, Marco Hietala, Ronnie Atkins, Sharon den Adel, Bob Catley, Robert Mason and Herbie Langhans.
Ghostlights scored the highest positions of any Avantasia release in several international music charts and even enabled Avantasia to enter the US Billboard charts for the second time. Another big world tour took place between March and August 2016.
Consisted of 40 concerts in Europe, North America, South America, Canada, Japan, Russia, and Scandinavia.
And with an exclusion of 8 headlining European summer festival performances, each show lasted for over 3 hours.
The ensemble was almost the same as on the previous tours, with the addition of Jorn Lande and Herbie Langhans.
After the completion of the tour, Avantasia headlined both Wacken Open Air and Barcelona Rock fest during the summer of 2017.
In 2018 Tobias Sammet posted on his Facebook that he started to work on an 8th Avantasia album.
And on February 15th Moonglow was released, with guest vocals by Jorn Lande, Bob Catley, Eric Martin, Ronnie Atkins, Michael Kiske, Geoff Tate, Candice Night, Hansi Kürsch and Mille Petrozza.
Moongow enter the German album charts on #1 for the first time.
The Moonglow tour took place between March and June 2019, consisting of 37 concerts across Europe, Japan, Australia, America, Canada, North America and South America.
And again, the shows will last 3 hours.