Triangulum is a small constellation in the northern sky. Its name is Latin for "triangle", derived from its three brightest stars, which form a long and narrow triangle. Known to the ancient Babylonians and Greeks, Triangulum was one of the 48 constellations listed by the 2nd century astronomer Ptolemy.
Celestial cartographers Johann Bayer and John Flamsteed catalogued the constellation's stars, giving six of them Bayer designations.
The white stars Beta and Gamma Trianguli of apparent magnitudes 3.00 and 4.00 respectively form the base of the triangle and yellow-white Alpha Trianguli, of magnitude 3.41, the apex. Iota Trianguli is a notable double star system, and there are three star systems with planets located in Triangulum. The constellation contains several galaxies, the brightest and nearest of which is the Triangulum Galaxy—a member of the Local Group. The first quasar ever observed, 3C 48, lies within Triangulum's boundaries.