Alpha Trianguli is a binary star system 63.3 light years from Sol.
The third UNSS Arcturus distinguished itself at the battle of Alpha Trianguli against Romulan forces during the Earth-Romulan War. ("The USS Arcturus in History")
The Treaty of Alpha Trianguli, ending the Earth-Romulan War, was negotiated by subspace radio. (TOS novel: The Romulan Way, Star Trek: Avenger: "The Essential Process")
In the 24th century, the system was the site of Starbase 310. (Star Trek Star Charts)