The Milky Way's nearest galactic neighbors range from massive spirals twice its size to a tiny, 5,000-light-year dwarf that it is actively eating alive.
These neighbors belong to the Local Group, a gravitationally bound collection of more than 50 galaxies spanning roughly 10 million light-years.
The Local Group is dominated by three major galaxies. The Andromeda Galaxy (M31) is the absolute heavyweight. Located 2.5 million light-years away, it spans an estimated 152,000 to 220,000 light-years in diameter—making it up to twice the size of the Milky Way, which measures roughly 100,000 light-years across. The Triangulum Galaxy (M33), the third-largest in the Local Group, is a more modest spiral measuring about 60,000 light-years in diameter.
However, the galaxies physically nearest to the Milky Way are its satellite galaxies. The most famous are the Magellanic Clouds, visible to the naked eye from the Southern Hemisphere. The Large Magellanic Cloud (LMC) measures about 14,000 light-years across, while the Small Magellanic Cloud (SMC) spans roughly 7,000 light-years. Despite their smaller stature compared to the Milky Way, they are complex systems packed with intense star-forming regions.
The title of nearest galaxy belongs to a pair of dwarf galaxies that are currently being consumed by the Milky Way. The Sagittarius Dwarf Spheroidal Galaxy sits just 70,000 light-years from Earth and measures roughly 10,000 light-years in diameter. Even closer is the Canis Major Dwarf Overdensity, located a mere 25,000 light-years away and spanning about 5,000 light-years. This structure has been stretched so severely by the Milky Way's tidal forces that astronomers continue to debate whether to classify it as a true dwarf galaxy or simply a long ribbon of stellar debris being woven into the Milky Way's galactic disk.