Nunki (Bayer designation Sigma Sagittarii) is the second brightest star in the constellation Sagittarius. Nunki has an apparent magnitude of +2.1 and belongs to the spectral classification B3.

Nunki can be eclipsed by the moon and very rarely by planets. The last coverage of Nunki by a planet took place on November 17, 1981, when it was eclipsed by Venus.

Coordinates (equinox 2000)

• Right ascension: 18h 52m 10s
• Declination: -26° 22' 00"