Milky Way

The Milky Way is the name the fleshlings have given to the galaxy Earth occupies. God only knows if Cybertron is in there or not.

Marvel Comics
Cybertron orbits the sun known as Alpha Centauri, located in the Milky Way.

Cartoon
Cybertron was originally quite some distance from Earth, possibly outside the Milky Way. However, the Decepticons later arranged for Cybertron to be drawn into Earth's orbit, bringing it firmly into the Milky Way galaxy. After that, travel between Earth and Cybertron was short (though it still consumed all of Omega Supreme's fuel).

Dreamwave
As in the Marvel Comics, Cybertron orbits the sun known as Alpha Centuari.

IDW
Cybertron is located in the Milky Way galaxy, located in the constellation Scorpius.