List of least massive black holes
Below there is a list of the least massive known black holes, sorted by increasing mass. The unit of measurement is the solar mass, equivalent to kg.
List
| Name | Mass | Distance | Companion class | Mass determination method | Notes | Refs. |
| 2MASS J05215658+4359220 | 10,000 | Spectroscopic radial velocity measurements of noninteracting companion. | In Milky Way outskirts. Recent Hubble ultraviolet data has suggested the companion to this object is actually a warm subgiant, and ruling out smaller compact companions such as a white dwarf. | |||
| GW190425's remnant | 518,600,000 | Gravitational wave data of neutron star merger from LIGO and Virgo interferometers. | 97% chance of prompt collapse into a black hole immediately after merger. Alternative study suggests collapse 2.5 hours later. | |||
| NGC 3201-1 | 15,600 | Spectroscopic radial velocity measurements of noninteracting companion. | In globular cluster NGC 3201. Companion is 0.8 main sequence turn-off. | |||
| GRO J1719-24/ GRS 1716−249 | 8,500 | Near-infrared photometry of companion and Eddington flux. | LMXB system. | |||
| 4U 1543-47 | 30,000 ± 3,500 | Spectroscopic radial velocity measurements of companion. | SXT system. | |||
| XTE J1650-500 | 8,500 ± 2,300 | Orbital resonance modeling from QPOs | Transient binary X-ray source | |||
| GRO J1655-40 | <5,500 | Precision X-ray timing observations from RossiXTE. | LMXB system. | |||
| GX 339-4 | 26,000 |