New experimental data for the thermal conductivity of 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone (Novec 649) are reported for vapor, liquid and supercritical states. These new experimental data were obtained with transient hot-wire apparatus over the temperature range from 183 K to 501 K and at pressures from 0.02 MPa to 69 MPa. These data were used to develop a wide-range correlation for the thermal conductivity of the vapor, liquid and supercritical fluid. The experimental data reported here have an uncertainty of 1 % for the liquid and supercritical regions (densities > 600 kg m-3), 1.5 % for vapor and supercritical regions (pressures ≥ 1 MPa and densities < 200 kg m-3), 3 % for supercritical states (200 kg m-3 ≤ densities ≤ 600 kg m-3), and 3 % for vapor and supercritical states (pressures < 1 MPa). The thermal-conductivity correlation developed in this work is estimated to have an expanded relative uncertainty, at a 95 % confidence level, ranging from approximately 1 % to 4 % that depends upon the temperature and pressure, with larger uncertainties in the critical region.