Abstract: In this talk I will demonstrate the potential of the black hole mass gap to probe new physics. The mass gap, in which no black holes can be formed, is a standard prediction of stellar structure theory. I will show that physics beyond the Standard Model may dramatically alter the late stages of stellar evolution, when it acts as an additional source of energy (loss) or modifies its equation of state. This results in variations in black hole populations, most prominently observable through shifts of the mass gap. The gravitational wave observations by the LIGO/Virgo collaboration will bring the edges of the black hole mass gap in sight in the coming years, making this an interesting novel probe of new physics.