The paper explores whether the black-hole (BH) binary detected by LIGO could be a signature of dark matter. It suggests that primordial black holes (PBHs) in the mass range 20M$_\odot$ to 100M$_\odot$ could constitute dark matter. If two PBHs in a galactic halo pass close enough, they emit gravitational waves that bind them, leading to a merger. The merger rate of PBHs is estimated to fall within the range inferred from GW150914, suggesting that LIGO may have detected PBH dark matter. PBH mergers are likely to be spatially distributed like dark matter and have no electromagnetic or neutrino counterparts. They can be distinguished from traditional BH mergers by their mass spectrum, high ellipticities, or stochastic gravitational wave background. Next-generation experiments could test these hypotheses. The paper also discusses uncertainties in the calculation and the potential observational signatures of PBHs. It concludes that while the possibility of LIGO detecting dark matter through PBH mergers is not ruled out, further observations and experiments are needed to confirm this.The paper explores whether the black-hole (BH) binary detected by LIGO could be a signature of dark matter. It suggests that primordial black holes (PBHs) in the mass range 20M$_\odot$ to 100M$_\odot$ could constitute dark matter. If two PBHs in a galactic halo pass close enough, they emit gravitational waves that bind them, leading to a merger. The merger rate of PBHs is estimated to fall within the range inferred from GW150914, suggesting that LIGO may have detected PBH dark matter. PBH mergers are likely to be spatially distributed like dark matter and have no electromagnetic or neutrino counterparts. They can be distinguished from traditional BH mergers by their mass spectrum, high ellipticities, or stochastic gravitational wave background. Next-generation experiments could test these hypotheses. The paper also discusses uncertainties in the calculation and the potential observational signatures of PBHs. It concludes that while the possibility of LIGO detecting dark matter through PBH mergers is not ruled out, further observations and experiments are needed to confirm this.