Yes—if you mean isotropic radiator, then an ideal, non-rotating black hole is about as close as nature gets to one.
An isotropic radiator emits the same power in every direction. A Schwarzschild black hole (non-rotating and uncharged) is perfectly spherically symmetric, so its Hawking radiation has no preferred direction. In that idealized case, the emission is isotropic.
There are a few qualifications:
- Rotating black holes are not perfectly isotropic because the spin axis defines a preferred direction.
- Charged black holes would also deviate from perfect isotropy.
- The emitted Hawking radiation is modified by spacetime curvature around the black hole (greybody effects), so the spectrum seen at infinity is not exactly that of an ideal blackbody.
In radio engineering terms, an isotropic radiator is a mathematical ideal used as a reference antenna. A Schwarzschild black hole is not literally an antenna, but its Hawking radiation is emitted with essentially the same angular symmetry as an ideal isotropic source.
Interestingly, if you are thinking about the Event Horizon Telescope images, the bright ring and asymmetry seen around black holes do not mean the black hole itself radiates anisotropically. Those features arise from the surrounding accretion flow, relativistic beaming, and gravitational lensing, not from the event horizon emitting more strongly in one direction than another.