Hexafluoro-1,3-butadiene (Sifren 46, Ausimont; ASHRAE Code R2316) is a fluoro compound with two double bonds in the molecule (C4F6) showing very high performance for plasma, ion beam, or sputter etching in semiconductor devices' manufacturing. Vapor pressures and compressed liquid densities of hexafluoro-1,3-butadiene have been measured at temperatures ranging from (263 to 343) K with pressures up to 7000 kPa. Saturated liquid densities have been extrapolated from isothermal compressed liquid density data. Vapor pressure has been measured by means of an apparatus based on a glass equilibrium cell, while density has been measured with a vibrating tube densimeter (Anton Paar DMA 512). For the vapor pressure measurements, the estimated accuracy is +/-1 kPa for pressure and +/-0.02 K for temperature. For the density measurements, the estimated accuracy is +/-0.02 K for temperature and +/-3 kPa for pressure. The densimeter has been calibrated by using 1,1,1,2-tetrafluoroethane (R134a) and vacuum. The overall estimated accuracy for the density data is within +/-0.1%.