aka NGC 598,The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum.
The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Milky Way and the Andromeda Galaxy (the largest). It is one of the most distant permanent objects that can be viewed with the naked eye.

It is sometimes informally referred to as the "Pinwheel Galaxy" by some amateur astronomy references, in some computerized telescope software, and in some public outreach websites.

Under exceptionally good viewing conditions with no light pollution, the Triangulum Galaxy can be seen with the 20/20 vision naked eye; to those viewers, it will sometimes be the farthest permanent entity visible without magnification. Its light diffuses (spreads) across a little more than a pinprick of the unmagnified sky, the cause of which is its broadness – this astronomers term a diffuse, rather than compact, object.

Observers range from finding the galaxy easily visible by direct vision in a truly dark (and impliedly dry, cloud-free) sky to needing to use averted vision in rural or suburban skies with good viewing conditions. It has been chosen as one of the critical sky marks of the Bortle Dark-Sky Scale.