Piotr Wiwczarek (born 22 October 1965 in Poland in Olsztyn), also known as Peter, (ex nickname Behemoth) is a Polish guitarist and vocalist who is the frontman for the death metal band Vader.He actually started out as their bassist. He is also a member of Bandid Rockin', Panzer X and Para Wino Band and is the producer of several of Vader's releases.

Piotr also became a producer for the first time in 1999 when producing the Polish death metal band Decapitated's first release, Winds of Creation.