NGC 3666

{{Short_description|Galaxy in the constellation Leo}}

{{Infobox galaxy

| name = NGC 3666

| image = File:NGC 3666 hst 09042 49 R814 B450.png

| caption = Hubble Space Telescope image of NGC 3666

| constellation name = Leo

| epoch = J2000

| type = SA(rs)c{{cite web| title=NASA/IPAC Extragalactic Database | url=http://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=26419&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1#BasicData_0|website=ned.ipac.caltech.edu | accessdate=3 June 2019 }}

| appmag_b = 12.5{{cite simbad|title=NGC 3666|access-date=3 June 2019}}

| ra = {{RA|11|24|26}}

| dec = {{DEC|+11|20|31}}

| z = 0.003536

| h_radial_v = {{nowrap|1018 ± 1 km/s}}

| names = NGC 3666, LEDA 35043, UGC 6420

}}

NGC 3666 is an unbarred spiral galaxy in the constellation Leo. It was discovered by William Herschel on March 15, 1784.{{cite web |last1=Seligman |first1=Courtney |title=New General Catalog Objects: NGC 3650 - 3699 |url=https://cseligman.com/text/atlas/ngc36a.htm#3666 |website=New General Catalog Objects: NGC 3650 - 3699 |accessdate=3 June 2019}} It is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.{{cite web | title=The Leo III Groups |work=Atlas of the Universe |url=http://www.atlasoftheuniverse.com/galgrps/leoii.html |access-date=2010-11-27 |archive-date=July 22, 2012 |archive-url=https://archive.today/20120722223749/http://www.atlasoftheuniverse.com/galgrps/leoii.html |url-status=live }}