What is Earth's nearest neighbor in space?

Earth’s nearest neighbor in space is the Moon.

The Moon is Earth’s natural satellite and the closest large celestial body to our planet. Its average distance from Earth is about 384,400 kilometers, or 238,900 miles, although that distance changes because the Moon follows a slightly elliptical orbit. At its closest, it is roughly 363,300 kilometers away; at its farthest, it is about 405,500 kilometers away.

The Moon’s gravity causes most of Earth’s ocean tides, especially through its interaction with the Sun’s gravity. The Moon is also tidally locked to Earth, meaning the same hemisphere generally faces us as it travels around our planet. This is why people often speak of the “far side” rather than the “dark side”: the far side receives sunlight too.

The Moon is not a planet, and it is not Earth’s only nearby object in every possible sense—small asteroids can pass closer temporarily. But for a standard astronomy question asking for Earth’s nearest natural neighbor, “the Moon” is the clear answer.