The Vance plan (Croatian: Vanceov plan, Serbian: Vensov plan) was a peace plan negotiated by the former United States Secretary of State Cyrus Vance in November 1991 during the Croatian War of Independence. At that time, Vance was the Special Envoy of the Secretary-General of the United Nations; he was assisted by United States diplomat Herbert Okun during the negotiations. The plan was designed to implement a ceasefire, demilitarize parts of Croatia that were under the control of Croatian Serbs and the Yugoslav People's Army (JNA), allow the return of refugees, and create favourable conditions for negotiations on a permanent political settlement of the conflict resulting from the breakup of Yugoslavia.

The Vance plan consisted of two agreements. The first agreement, known as the Geneva Accord, was signed by Yugoslav defence minister General Veljko Kadijević, President of Serbia Slobodan Milošević and Croatian President Franjo Tuđman in Geneva, Switzerland, on 23 November 1991. Because the ceasefire agreed at that time did not hold, further negotiations resulted in the Implementation Agreement of 2 January 1992. The Implementation Agreement, signed in Sarajevo, Bosnia and Herzegovina, by JNA Lieutenant Colonel General Andrija Rašeta and Croatian defence minister Gojko Šušak, produced a longer-lasting ceasefire, which was supervised by the United Nations Protection Force (UNPROFOR). The parties failed to completely implement the remaining major aspects of the Vance plan.

In August 1990, an insurgency known as the Log Revolution took place in Croatia. It centred on the predominantly Serb-populated areas of the Dalmatian hinterland around the city of Knin, parts of the Lika, Kordun, and Banovina regions, and settlements in eastern Croatia with significant Serb populations. These areas were subsequently declared to be the Republic of Serbian Krajina (RSK). After the RSK declared its intention to join Serbia, the Government of Croatia declared the RSK a rebel organization. By March 1991, the conflict had escalated, resulting in the Croatian War of Independence. In June 1991, Croatia declared its independence as Yugoslavia disintegrated. A three-month moratorium on the declarations of independence by Croatia and the RSK followed, but both declarations came into effect on 8 October.

The Croatian National Guard (Croatian: Zbor narodne garde, ZNG) was formed in May 1991 because the Yugoslav People's Army (Serbo-Croatian: Jugoslovenska Narodna Armija, JNA) increasingly supported the RSK and the Croatian Police were unable to cope with the situation. In November the same year, the ZNG was renamed the Croatian Army (Croatian: Hrvatska vojska, HV). The establishment of the military of Croatia was hampered by a UN arms embargo that had been introduced in September. The final months of 1991 saw the fiercest fighting of the war, culminating in the Battle of the Barracks, the Siege of Dubrovnik, and the Battle of Vukovar.

The Vance plan was a result of a diplomatic mission by Cyrus Vance, the former United States Secretary of State, then Special Envoy of the Secretary-General of the United Nations. He was assisted by US diplomat Herbert Okun and Under-Secretary-General of the United Nations for Special Political Affairs Marrack Goulding. The mission was sent to SFR Yugoslavia and was aimed at negotiating the end of hostilities in Croatia in late 1991. The plan proposed a ceasefire, protection of civilians in specific areas designated as United Nations Protected Areas and a United Nations (UN) peacekeeping operation in Croatia.

The plan was first presented to the President of Serbia, Slobodan Milošević. Milošević found the plan wholly acceptable and promised he would ensure the leadership of the RSK eventually supported it. He endorsed the plan because it ensured the preservation of Serbian territorial gains of 1991, retained Croatian Serb administration of the areas where the peacekeepers would be deployed and allowed the JNA to shift its focus to Bosnia and Herzegovina. Vance then met Yugoslav defence minister JNA General Veljko Kadijević, who also endorsed the plan and was apparently urged by Milošević to do so. After the plan was accepted by Croatian President Franjo Tuđman, the Geneva Accord was signed by Tuđman, Milošević and Kadijević in Geneva, Switzerland, on 23 November 1991. The Accord was a precondition for the deployment of the UN peacekeeping force. It comprised four provisions; the end of the Croatian blockade of JNA barracks, the withdrawal of JNA personnel and equipment from Croatia, the implementation of a ceasefire and the facilitation of the delivery of humanitarian aid.

The parties to the accord also agreed to the deployment of a UN peacekeeping mission in Croatia, which was later authorized through United Nations Security Council Resolution 721 of 27 November, following a formal request for deployment of the peacekeepers submitted by the Yugoslav government the previous day.

The Vance plan was approved pursuant to UN Security Council Resolution 721 as a part of the Report of the UN Secretary-General submitted on 11 December, as UN Security Council Resolution 724 of 15 December. That resolution determined that the conditions necessary to deploy the peacekeepers had not yet been met. Instead, the UN deployed 50 liaison officers to prepare the mission while fighting continued throughout 1991. The blockade of JNA barracks in HV-controlled territory remained in place until December 1991.