Mariëtte Iris Hamer (born 7 June 1958) is a Dutch politician and trade union leader serving as commissioner for combating inappropriate behavior and sexual violence since 2022.

Since 10 September 2014 Hamer has been a Crown-appointed member and Chairwoman of the Social and Economic Council (SER).

She was nominated to the position by Lodewijk Asscher, Minister of Social Affairs and Employment; King Willem-Alexander of the Netherlands validated the appointment.

She succeeded Wiebe Draijer, who resigned from office following his appointment as CEO of the Rabobank.

She recommended colleges and universities to provide mandatory sex education, to hire ombudsmen, and to better inspect student associations.