In the Star Wars universe, the Peace Brigade was a band of sentient beings that assisted the Yuuzhan Vong in their war against the people of the Star Wars galaxy.
They thought that the Vong would ultimately win the war against the New Republic and the other governments of the galaxy. They engaged in disruption of governments, capturing government officials, helping the Vong to enslave others, and helping the Vong capture Jedi. The Peace Brigade would also ferry weapons for the Vong and help with other tasks - especially those that required interaction with mechanical technology.
Initially a loose coalition of like minded beings, the Peace Brigade later coalesced into a centrally managed group that worked much like Black Sun or the Bothan Spynet. By then the galaxy realized that the Yuuzhan Vong could not be trusted to show mercy, and the Yuuzhan Vong were enslaving members of the brigade and sending them off to fight.
At the conclusion of the war, the victorious Galactic Federation of Free Alliances - the successor state to the New Republic - put the surviving high ranking members of the brigade on trial for treason and war crimes.