Which major galaxy is predicted to collide with the Milky Way in the future?

The Andromeda Galaxy is the major galaxy predicted to collide with the Milky Way in the distant future.

Andromeda, also called Messier 31 or M31, is the nearest large galaxy to the Milky Way and the largest member of the Local Group. Its motion toward us is measured partly through its blueshift, while observations also track its sideways movement across the sky.

Older simulations commonly placed a likely galactic encounter roughly 4–5 billion years from now. A collision would not mean stars crashing together like cars: the distances between stars are enormous, so direct stellar impacts would be rare. Gravity would instead distort both galaxies, trigger some star formation, and eventually produce a merged remnant.

Recent Gaia and Hubble-based studies have lowered confidence in a definite head-on collision, so “predicted” is more accurate than “certain.” The Whirlpool, Sombrero, and Triangulum galaxies are different objects; Triangulum may interact with the pair, but it is not the principal galaxy named in this prediction.