Sinus Lunicus (; Latin for "Bay of Lunik") is an area of lunar mare along the southeast edge of the Mare Imbrium on the Earth's Moon. It is formed by the area enclosed by the prominent craters Archimedes to the southwest, Autolycus to the southeast, and Aristillus to the northeast. The bay is open to the northwest, and faces the Montes Spitzbergen, a small chain of mountains.
thumb|left|Location of Sinus Lunicus on the Moon
This bay was named the Bay of Lunik by the International Astronomical Union (IAU) in 1970 to honor the landing site of Luna 2,