We assess the thermal conductivity of the Earth’s lower mantle anchored on our first-principles calculations of lattice thermal conductivity of MgSiO3 perovskite. Our calculations agree with measurements of iron-free perovskite at ambient conditions and show a lower pressure dependence compared with other recent calculations. In addition, we show that the effect of iron on the lattice thermal conductivity of silicate perovskite is likely to be small at high temperatures. To provide an assessment of thermal...