Johannes Juliaan Gijsbert "Hans" Jansen (Dutch pronunciation: [joːˈɦɑnəs ˈjyliaːn ˈɣɛisbɛrt ˈɦɑns ˈjɑnsən]; 17 November 1942 – 5 May 2015) was a Dutch politician, scholar of contemporary Islam and author. Hans Jansen belonged to the "revisionists" in Islamic Studies, i.e. he fundamentally doubted the historicity of the Islamic traditions on early Islam which were written only 150 to 200 years after Muhammad. Moreover, Jansen doubted the existence of Muhammad as a historical person.