The Khitomer Conference was the first full peace negotiations between the United Federation of Planets and the Klingon Empire in 2293, held at Camp Khitomer, a Klingon colony on the planet Khitomer near the border with the Federation.
Following the destruction of the Klingon moon of Praxis, Chancellor Gorkon reached out to the Federation for détente and an end to the lengthy and costly hostilities between the two superpowers. Following Gorkon's assassination by anti-peace operatives from Starfleet, his daughter, Azetbur, became chancellor and continued her father's peace initiative. For security reasons, the location of the conference was kept secret. However, both sides underestimated the extent of the Khitomer conspiracy. Eventually, personnel from the USS Enterprise-A and the USS Excelsior intervened, preventing an assassination attempt against the Federation President and exposing the conspiracy.
Ultimately, the Khitomer Conference led to the signing of the Khitomer Accords and the beginnings of nearly a century of peace between the Federation and the Klingon Empire. (Star Trek VI: The Undiscovered Country)
Captain Spock and Ambassador Pardek first met during the Khitomer conference and began setting forth the goal of reuniting the Vulcan and Romulan governments. (TNG: "Unification I")
One of the Federation ambassadors present at the conference was Curzon Dax. (DS9: "You Are Cordially Invited")
One of Chancellor Azetbur's delegation members was Colonel Worf. (Star Trek VI: The Undiscovered Country)