Guus Janssen (born 13 May 1951 in Heiloo, North Holland) is a Dutch composer of contemporary music and a recording artist. A pianist and harpsichordist, he is also active as a jazz performer. He studied piano and composition at the Sweelinck Academy of Music in Amsterdam with Ton de Leeuw (composition) and Jaap Spaanderman (piano). He also studied piano with Ton Hartsuiker. He has performed with John Zorn, George Lewis, Han Bennink, Theo Loevendie, and Gidon Kremer.