P'Jem was a Vulcan monastery which was located on a planet near the Vulcan-Andorian border. The monastery was established in the 9th century BCE. One of the founders was Master Haadok, who was buried in the catacombs beneath the monastery when he died.
In 2151, a team of Andorians led by Shran invaded the monastery, and took the monks prisoner. When a team consisting of Captain Jonathan Archer, Subcommander T'Pol, and Commander Charles Tucker III visited the monastery, they were also taken prisoner by the Andorians. Eventually managing to escape custody, they found that a covert listening post had been placed in the catacombs to be used against the Andorians. Upon discovering this, Jonathan Archer gave the data on the listening post to the Andorians. (ENT episode: "The Andorian Incident")
The Andorians decided several months later to destroy the monastery and listening post. In response, the Vulcans nearly canceled joint Earth-Vulcan fleet operations. Blaming T'Pol for the destruction of the monastery, the Vulcan High Command recalled her, but later rescinded this after her actions in the Coridan system. (ENT episode: "Shadows of P'Jem")
Even though T'Pol was allowed to continue in her position on board the Enterprise (NX-01), the High Command still retaliated against her family. T'Pol's mother T'Les was stripped of her position at the Vulcan Science Academy when charges of treason were fabricated against her. T'Pol then had to marry Koss in an effort to help her mother regain her position. (ENT episode: "Home")
During the Borg Invasion of 2381, a number of Vulcans and Vulcanoids were evacuated to P'Jem. After the invasion ended, a delegation of Médecins Sans Frontières doctors, including Ayib Yee Pran, arrived to treat the survivors. (ST novel: A Singular Destiny)
By 2409, the monastery had been completely rebuilt. In that year, Ambassador Sokketh was to be taken to P'Jem aboard a Starfleet vessel, but had been replaced by a member of the Undine. When discovered, it reverted to its natural form and attacked those around it. (STO mission: "Diplomatic Orders")
In the mirror universe, General Shran destroyed the P'Jem monastery in retaliation for a rebel assault on Earth. The assault was carried out for propaganda purposes only. (ENT novel: Age of the Empress)