109 Piscium b is an extrasolar planet, discovered on November 14, 1999. It is at least 6.38 times the mass of Jupiter, and it very likely is a gas giant. It orbits its host star, 109 Piscium every 1076 earth days.

It is estimated that the planets effective temperature is 264 K (-9.15 °C, 15.53 °F), but it might be 10 or 20 K higher due to internal heating.

Preliminary astrometric measurements suggested that the orbital inclination is 170.3°, yielding an object mass of 38 times that of Jupiter, which would make it a brown dwarf. However, subsequent analysis indicates that the precision of the measurements used to derive the astrometric orbit is insufficient to constrain the parameters, so the true inclination and mass remain unknown.

A more plausible suggestion is that this planet shares its star's inclination, of 69°.