The Moonsorrow saga began in late 1995, when the cousins Henri and Ville Sorvali got together with the idea of creating folkish, epic metal art. The first demo Thorns of Ice was recorded in early 1996; fairly enough, half of the material disappeared, so the tape was never released.

In spring 1997 Moonsorrow released Metsä, the demo that is generally considered the debut recording of the band, gaining some publicity in the press and a small fanbase. Also another tape, bluntly called Promo, was recorded, but due to a divine (analog) intervention it was never released either.

Through 1998 the band worked on their next demo, Tämä Ikuinen Talvi, which was later released in early 1999. This was to be the last demo recording in Moonsorrow's history, since a deal with obscure Plasmatica Records was inked shortly afterwards. Marko Tarvonen joined the band as the third member, and Moonsorrow was ready for the debut album.
And so the debut album was recorded, in February 2000. No one knew it would take more than a year to be released, though. In the meantime also Mitja Harvilahti and Markus Eurén joined Moonsorrow (initially as session members) and so the band was ready for live shows as well. The first gig took place, ironically, in the Turku metropolis.

Approaching the summer of 2001, the debut album Suden Uni was finally released, and Moonsorrow was already working on the follow-up. Signed a fresh contract with Spikefarm Records, Voimasta ja Kunniasta was released at the end of the same year. In the meantime Sagitarius Productions also released a partial remake of Tämä Ikuinen Talvi on cd format, eventually exceeding the sales of the original (sold-out) recording; inspired by this, Moonsorrow also partially remade Metsä and offered it to their fans as a free download in 2002.

The third full-length Kivenkantaja was recorded in late 2002, offering a new progressive edge to Moonsorrow's epic heathen metal; as supposedly the most difficult Moonsorrow album to digest, it eventually climbed onto position 16 at the Finnish charts in its release week in 2003. Following this hint of success, Moonsorrow took a deserved break and wouldn't return with a new album until 2005.

However, the negotiations between Spikefarm and Plasmatica concerning the reissue of Suden Uni were finally closed shortly after the release of Kivenkantaja. In late 2003, the newly wrapped, remastered debut album was released with a bonus track and a bonus dvd, slightly blurring the ongoing intermission.

In 2004 Moonsorrow returned powerfully with a few live shows, including their first ever abroad, curiously in Croatia. Writing new material intensively for the whole summer, the band finally entered the studio in September to record Verisäkeet, by far their most obscure and intriguing album to date.

Verisäkeet was released in early 2005, and was well received by all fans. It is over 70 minutes long, yet contains only 5 tracks, and is their most epic album to date. The band then embarked on their most adventurous tour, notably making an appearance in January 2006 at the Heathen Crusade Festival in Minnesota, USA. They have since signed a new 2-album contract with Spikefarm Records.

With only two tracks their fifth album "V: Havitetty", released in 2007, furthered the band's reputation as one of the most unconventional and, certainly, one of the most epic folk metal bands around. The EP "Tulimyrsky" was released in 2008 and boasted a couple re-recordings and covers, including a cover of "For Whom the Bell Tolls" by Metallica.