The Lachin corridor (Azerbaijani: Laçın dəhlizi, Armenian: Բերձորի միջանցք, Berdzori mijantsk) was a mountain road in Azerbaijan that linked Armenia and Nagorno-Karabakh.

Being the only road between these two territories, it was considered a humanitarian corridor or "lifeline" to the Armenian population of Nagorno-Karabakh. Until Armenia secured the Lachin corridor in 1992, the Armenians of Nagorno-Karabakh were entirely isolated, relying solely on their own limited resources and aid flown in from Armenia. At that time, humanitarian aid from the Red Cross, the UN, and France were blocked by Azerbaijani authorities.

Following the 2020 Nagorno-Karabakh ceasefire agreement, Armenia conceded control of the corridor to a Russian peacekeeping force. In 2022, the government of Azerbaijan re-imposed a siege of Nagorno-Karabakh which involved blocking the Lachin corridor. These actions were criticized by numerous countries, international organizations and human rights groups, many of which considered them to be a violation of the ceasefire agreement that ended the Second Nagorno-Karabakh War.

On 23 April 2023, Azerbaijani officials set up a checkpoint in the corridor, claiming it was meant to prevent "illegal" transport of military supplies and natural resources, however, the republics of Armenia and Artsakh denied these allegations and the ceasefire agreement did not explicitly limit the use of the Lachin corridor to humanitarian needs. After a military offensive in September 2023, Azerbaijani forces took control of the entirety of Nagorno-Karabakh, after which nearly all of the region's Armenian population fled to Armenia through the Lachin corridor.

During the First Nagorno-Karabakh War, Nagorno-Karabakh and neighbouring Armenia were blockaded in August 1989, with Azerbaijan severing transport and economic links both between Armenia and Azerbaijan and between Nagorno-Karabakh and Armenia. In May 1992, forces of the Nagorno-Karbakh Republic captured Lachin and established a land connection with Armenia, ending the blockade. After the end of the war, the status of the Lachin corridor was one of the major issues of the peace negotiations between Armenia and Azerbaijan. Various configurations were proposed for the status of the corridor. In one round of negotiations in 1999, it was proposed that Azerbaijan would accept Armenian control over the corridor in exchange for a land corridor through southern Armenia to connect it to its exclave Nakhchivan. In a statement to the United Nations on 18 September 2005, Foreign Minister of Azerbaijan Elmar Mammadyarov stated that Azerbaijan was in favor of the deployment of a multinational peacekeeping force "at the initial stage" to ensure security along the Lachin corridor for bilateral use.

In the aftermath of the Second Nagorno-Karabakh War, which ended with a Russian-brokered armistice, the Lachin corridor became the sole connection between Armenia and Nagorno-Karabakh. The armistice agreement provided:

The Republic of Armenia shall return [...] the Lachin District by December 1, 2020. The Lachin Corridor (5 km wide), which will provide a connection between Nagorno-Karabakh and Armenia while not passing through the territory of Shusha, shall remain under the control of the Russian Federation peacemaking forces.

As agreed by the Parties, within the next three years, a plan will be outlined for the construction of a new route via the Lachin Corridor, to provide a connection between Nagorno-Karabakh and Armenia, and the Russian peacemaking forces shall be subsequently relocated to protect the route.