The Trillian government was the government of the symbionts and Trill people, responsible for upholding Trill law. In 3189, Leader Pav was head of the Trillian government, which at the time, was not a member of the United Federation of Planets. (DIS: "Forget Me Not")
In 2369, the government believed, as a Trill – namely, Jadzia Dax – was involved in an extradition hearing, a Trill should be present during the hearing. The Trill, Selin Peers, was one of Commander Benjamin Sisko's witnesses in the hearing and testified as an expert in Trills. (DS9: "Dax")
Travelling to Trill in 3189, the USS Discovery's planetary catalog made reference to the Trillian government among other active agencies on the planet. The Discovery made contact with both Commissioner Vos and Leader Pav of the Trillian government. (DIS: "Forget Me Not")