The Moon
The Moon's rotation period is precisely equal to its period of revolution around the Earth (27.3 days), so the Moon always keeps the same side facing Earth. To an astronaut standing on the Moon's near-side surface, Earth would appear stationary in the sky (although its daily rotation would be clearly evident). This condition, in which the spin of one body is precisely equal to (or synchronized with) its revolution around another body, is known as a synchronous orbit. The fact that the Moon is in synchronous orbit about the Earth is no accident. It is an inevitable consequence of the gravitational interaction between those two bodies.