Simen Hestnæs (born March 4th, 1974, in Oslo, Norway), also known as I.C.S. Vortex, or simply Vortex, is the current vocalist and bassist of the progressive black metal band Borknagar and the vocalist and guitarist of the doom metal band Lamented Souls. Previously he has also been the vocalist of avant-garde metal band Arcturus and the bassist and background vocalist of the symphonic black metal band Dimmu Borgir.

In 2011, Simen Hestnæs began his solo project. He is also in a new band called Artisan, featuring Mustis (ex-Dimmu Borgir) on keyboards, Asgeir Michelson (Spiral Architect) on drums, Jens F. Ryland (Borknagar) on guitars and Vortex himself on vocals and bass.