A turbocharger includes an annular bypass passage to allow exhaust gas to bypass the turbine wheel. An annular bypass valve is disposed in the bypass passage. The bypass valve comprises a fixed annular valve seat and a rotary annular valve member arranged coaxially with the valve seat. The valve member is disposed against the valve seat and is rotatable about the axis for selectively varying a degree of alignment between respective orifices in the valve seat and valve member. The turbine includes a nozzle having a vane assembly. In one embodiment the vane assembly has only fixed vanes. In another embodiment the vane assembly includes both fixed vanes and variable vanes, and the variable vanes are part of a rotor that rotates together with the rotary valve member.