NGC 2121 (also ESO 57-SC40) is a magnitude +12.4 open cluster located in the constellation Mensa.
The cluster was discovered by British astronomer John Herschel using a 47.5 cm (18.7 inch) reflecting telescope at the Cape of Good Hope on the 9th February 1836.
Right Ascension 05h 48m 12.4s, Declination -71° 28' 52"
