Chairman Gregoroth is the Chairman of the Imperial Senate in Final Fantasy XII.
Following the destruction of the Leviathan, the Senate, under Gregoroth's leadership, forces Emperor Gramis to dismiss Vayne Solidor as Consul of Rabanastre and re-call him to Archades, where he is to stand trial for his misuse of the Imperial Fleet.
Following Vayne's return the Emperor is murdered. Vayne and the Ministry of Law blame the Senate, and accuse Gregoroth of heading this conspiracy. According to Vayne and the Ministry, Gregoroth confessed the murder and then committed suicide. However, it is strongly implied that it was Vayne who actually killed the Emperor, only to later blame the Senate. Whether Gregoroth actually committed suicide or was instead killed by Vayne and his minions is unknown.