Known black holes

A list of currently known black holes. Although you can't see black holes, it is nonetheless interesting to know which constellations they are found in.

Black holes (BHs) are formed by the gravitational core collapse of massive stars during a Type II supernova. As such, they are dead (degenerate) because they no longer generate fusion. Most galaxies in the universe have a supermassive black hole at their center. And there are two trillion galaxies in the observable universe. As such, this list only includes the smaller black holes thus far found in our galaxy, with a couple of notable exceptions:

Sgr A* - supermassive black hole at the center of our Milky Way galaxy
M87* - supermassive black hole at the center of the Virgo A galaxy (first BH imaged)

HR 6819 is actually a black hole and two stars forming a trinary system. These stars are visible to the naked eye.

Manatee Nebula Aquila
SS 433 stellar Aquila
V1487 Aql stellar Aquila
W49B Aquila
V821 Ara stellar Ara
XTE J1650-500 stellar Ara
CXOU J132527 stellar Centaurus
Cygnus X-1 stellar Cygnus
Cygnus X-3 stellar Cygnus
V404 Cyg stellar Cygnus
LB-1 stellar Gemini
IL Lupi stellar Lupus
V616 Mon stellar Monoceros
GU Mus stellar Musca
V381 Nor stellar Norma
Great Annihilator intermediate Ophiuchus
Messier 15 intermediate Pegusus
GRO J0422+32 stellar Perseus
HLX-1 intermediate Phoenix
SN 1997D stellar Recticulum
GCIRS 13E intermediate Sagittarius
Sagittarius A* supermassive Sagittarius
V4641 Sgr stellar Sagittarius
IGR J17091-3624 stellar Scorpius
V1033 Sco stellar Scorpius
HR 6819 stellar Telescopium
M33 X-7 stellar Triangulum
KV UMa stellar Ursa Major
M82 X-1 intermediate Ursa Major
SDSS J120136 double Ursa Major
M87* SMB Virgo
PKS 1302-102 double Virgo
QZ Vul stellar Vulpecula