Wouter Koolmees (born 20 March 1977) is a Dutch economist and politician and of the Democrats 66 (D66) party who served as Minister of Social Affairs and Employment in the Third Rutte cabinet from 2017 to 2022.

He also served as second Deputy Prime Minister of the Netherlands from 2019 to 2020 during Kajsa Ollongren's medical leave of absence.

Koolmees was a member of the House of Representatives from 17 June 2010[2] until his ministerial appointment on 26 October 2017; as a parliamentarian, he focused on matters of finance, transport and water supply.

On 26 October 2017, he assumed office as Minister of Social Affairs and Employment, succeeding Lodewijk Asscher.

Following the 2021 national elections, Koolmees and Tamara van Ark of the VVD were chosen to lead their parties' negotiations on a coalition agreement.