45 Cancri is a binary star system in the zodiac constellation of Cancer, located 680 light-years away from the Sun. It has the Bayer designation A1 Cancri; 45 Cancri is the Flamsteed designation. It is visible to the naked eye as a faint, white-hued star at an apparent visual magnitude of 5.62. The pair form a double-lined spectroscopic binary with an orbital period of 1009.36d and an eccentricity of 0.46. They are drifting closer to the Earth with a heliocentric radial velocity of −6 km/s.
The primary, designated component A, is an aging giant star with a stellar classification of G8 III, but has most likely not yet made multiple ascents up the red giant branch. It has 3.11 times the mass of the Sun and has expanded to 14 times the Sun's radius. The star is radiating 210 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of . The less evolved secondary, component B is likewise a giant star, having a class of A3 III. It has three times the mass of the Sun and shines with 191 times the Sun's luminosity.