United Nations Security Council resolution 621, adopted unanimously on 20 September 1988, after hearing a joint report by the Secretary-General and Organisation of African Unity (OAU), the Council noted an agreement between Morocco and the Frente Polisario on 30 August 1988 to the joint proposals by the Secretary-General and OAU.

The Council noted its anxiety to those efforts to support a referendum for self-determination of the people of Western Sahara, organised and supervised by the United Nations in conjunction with the OAU. In this vein, the resolution decided to appoint a Special Representative for Western Sahara, requesting the Secretary-General to transmit a report on the holding of a referendum in Western Sahara and ways to ensure the organisation of such a referendum by the UN and OAU.

• History of Western Sahara
• List of United Nations Security Council Resolutions 601 to 700 (1987–1991)
• Polisario Front
• Sahrawi Arab Democratic Republic
• United Nations Mission for the Referendum in Western Sahara

• Text of the Resolution at undocs.org

• Works related to United Nations Security Council Resolution 621 at Wikisource