X-ray diffraction of SnO2 (cassiterite) at high pressures and temperatures demonstrates the existence of four phase transitions to 117 GPa. The observed sequence of phases for SnO2 is rutile-type (P42∕mnm)→CaCl2-type(Pnnm)→pyrite-type(Pa3̅ )→ZrO2 orthorhombic phase I (Pbca)→cotunnite-type (Pnam). Our observations of the first three phases are generally in agreement with earlier studies. The orthorhombic phase I and cotunnite-type structure (orthorhombic phase II) were observed in SnO2 for the first time. The Pbca phase is found at 50–74 GPa during room-temperature compression. The cotunnite-type structure was synthesized when SnO2 was compressed to 74 GPa and heated at 1200 K. The cotunnite-type form was observed during compression between 54–117 GPa with additional laser heating carried out at 91 and 111 GPa. Fitting the pressure-volume data for the high-pressure phases to the second-order Birch-Murnaghan equation of state yields a bulk modulus of 259(26) GPa for the Pbca phase and 417(7) GPa for the cotunnite-type phase.