Guus Janssen (born 13 May 1951) 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 and piano with Jaap Spaanderman.

[1] He has performed with John Zorn, George Lewis, Han Bennink (and Bennink's group Clusone Trio as a guest), Theo Loevendie, and Gidon Kremer.

He composed two operas in collaboration with Friso Haverkamp and has released several CDs.