Milky Way

The Milky Way's closest neighbor is the Canis Major Dwarf.

An excerpt from the article 16 facts about Milky Way

This dwarf galaxy is located 42.000 years ago. light years from the center of our galaxy and 25 thousand. light years from the solar system. It was discovered in November 2003 because it is hidden behind the Milky Way's clouds of dust and gas. It contains about 100 million stars and is currently being torn apart by our galaxy's gravity.