NGC 3666 (also MCG 2-29-25, UGC 6420 and PGC 35043) is a magnitude +11.7 barred spiral galaxy located 49 million light-years away in the constellation Leo.
The galaxy was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Datchet, Berkshire, on the 15th March 1784.
Right Ascension 12h 25m 50.5s, Declination Dec +10° 27' 32"
