We calculate the three-loop thermodynamic potential of QCD at finitetemperature and chemical potential using the hard-thermal-loop perturbationtheory (HTLpt) reorganization of finite temperature and density QCD. Theresulting analytic thermodynamic potential allows us to compute the pressure,energy density, and entropy density of the quark-gluon plasma. Using these wecalculate the trace anomaly, speed of sound, and second-, fourth-, andsixth-order quark number susceptibilities. For all observables considered wefind good agreement between our three-loop HTLpt calculations and availablelattice data for temperatures above approximately 300 MeV.