Piotr Paweł Wiwczarek (born 22 October 1965 in Olsztyn, Poland), also known as Peter, (ex nickname Behemoth) is a Polish musician who is the vocalist and lead guitarist for the death metal band Vader, as the only constant member of the band since its inception. He has also collaborated with Kazimierz "Para" Paraszczuk on his tribute album, Bandid Rockin', and is the producer of several of Vader's releases. He is also the founder and guitarist of a side-project, named Panzer X.
Wiwczarek also became a producer for the first time in 1999, when producing the Polish death metal band Decapitated's first release, Winds of Creation.