Flemming 'Razz' Rasmussen (born 1958) is a Danish engineer, producer and owner and founder of Sweet Silence Studios in Copenhagen, Denmark. Throughout his career, he's worked mainly on metal, making his reputation as the engineer and producer (with the band) of Metallica's albums Ride the Lightning (1984), Master Of Puppets (1986) and ...And Justice For All (1988). While he received critical acclaim for the first two, the mix of ...And Justice for All got a mixed reception. It was the last work he would do with the band.

He also produced the Morbid Angel album Covenant, Blind Guardian's albums Imaginations from the Other Side, The Forgotten Tales, and Nightfall in Middle-Earth, Artillery's By Inheritance and Ensiferum's Iron, amongst others.

Rasmussen won a Grammy for producing Metallica's "One" in 1989. In 1994, the Danish Grammys recognized him as producer of the year for his work on Sort Sol's Glamourpuss.

In 2007, he produced English thrash metal band Evile's debut album Enter the Grave on Earache Records.