Jacobus Gijsbert "Koos" Rietkerk (14 December 1927 – 20 February 1986) was a Dutch politician of the People's Party for Freedom and Democracy (VVD) and jurist.

After the election of 1971 Rietkerk was appointed as State Secretary for Social Affairs in the Cabinet Biesheuvel I, taking office on 28 July 1971.

Rietkerk returned as a Member of the House of Representatives following the appointment of Henk Vonhoff as Mayor of Utrecht, he resigned as General-Secretary of the Industry and Employers' association on 1 September 1974 taking office on 11 September 1974 again serving as a frontbencher and spokesperson for Justice, Social Affairs and the Ombudsman.

After the election of 1982 Rietkerk was appointed as Minister of the Interior in the Cabinet Lubbers I, taking office on 4 November 1982.

On 20 February 1986 Rietkerk died after suffering a fatal Heart attack during a meeting in his office at the Ministry of the Interior at the age of 58.