Gauge/gravity duality can be used to study QCD at high densities and low temperatures where many other theoretical tools do not work and uncertainties are therefore large. I will review recent progress on this topic, including modeling of both the nuclear and the quark matter phases, which may appear in neutron star cores and in neutron star mergers. Holographic results for viscosities and conductivities differ significantly from pertubative QCD predictions in the dense quark matter phase, highlighting the differing transport properties of weakly and strongly interacting systems. I also discuss applications of the holographic equation of state to isolated (static and rotating) neutron stars, as well as to neutron star mergers.