New experimental data on the thermal conductivity of 1,1,1,3,3-pentafluoropropane (R245fa) are reported that cover a wide range of liquid conditions. These new experimental data were made with a transient hot-wire apparatus and cover the liquid phase over a temperature range of 173-344 K and a pressure range of 0.1-71 MPa. The experimental data reported here have an expanded uncertainty (0.95 level of confidence) of less than 1%. The measurements are used with selected literature data to develop correlations for the thermal conductivity. On the basis of this expanded uncertainty and comparisons with experimental data, the thermal conductivity correlation for R245fa is estimated to have a relative expanded uncertainty (0.95 level of confidence) of about 2% at a 95% confidence level for the liquid phase at pressures to 70 MPa and 2% for the vapor phase. In addition, we surveyed literature data and developed a correlation for the viscosity of R245fa. The estimated relative expanded uncertainty (0.95 level of confidence) of this correlation is 3% for the liquid phase at pressures to 40 MPa and 2% for the vapor phase.