Niklas Sundin

In Dark Tranquillity, he was one of only two members (the other being drummer Anders Jivarp) to maintain his musical role, unlike the other members who have or had switched. He also wrote some of the lyrics for the first three and recent two Dark Tranquillity albums (Lead singer Mikael Stanne wrote all of Dark Tranquillity's lyrics from Projector through Fiction) and In Flames' album The Jester Race, and continued to translate In Flames vocalist Anders Fridén's lyrics from Swedish to English for the next few albums while Anders worked to become more proficient in English. Although he quit Dark Tranquillity in 2016, it wasn't announced until 22 March 2020.

His main guitars are Gibson Faded SG, Gibson 1983 Flying V, and an Ibanez IC400; he also uses a custom J. Nunis SC1, 2 Gibson Les Pauls (Standard and Gothic), and a Fender Talon I. He previously used Rocktron Chameleon rack mounted pre-amplifiers, but after the Damage Done tour, he and Martin Henriksson began using Peavey 5150 and Mesa/Boogie Dual Rectifier amplifiers along with Behringer V-AMP 2 modeling processors. In the making of We Are the Void, they are seen in the studio using a Peavey 6505, an ENGL Powerball, as well as a Bugera amplifier.. He also endorses Mayones Guitars & Basses.

Niklas Sundin (born 13 August 1974 in Sweden), is a musician of the band Mitochondrial Sun, but was best known as the lead guitarist of band Dark Tranquillity (1989–2016). He was also one of the guitarists in the band Laethora (2005–2010).