A turbocharger comprising: a compressor including a compressor housing; a turbine housing defining at least part of a generally annular chamber extending circumferentially about a longitudinal axis of the turbine housing, the turbine housing defining a bore extending along the longitudinal axis; a turbine wheel disposed in the turbine housing; a nozzle passage leading from the chamber radially inwardly into the turbine wheel; the turbine housing defining an annular bypass volute surrounding the bore and arranged to allow exhaust gas to bypass the turbine wheel; an annular bypass valve disposed in the bypass volute, the bypass valve comprising a fixed annular valve seat and a rotary annular valve member, the valve member being disposed against the valve seat and being rotatable about the longitudinal axis for selectively varying a degree of alignment between respective orifices (73, 75) defined through each of the valve seat and valve member, ranging from no alignment defining a closed condition of the bypass valve, to at least partial alignment defining an open condition of the bypass valve; a rotary drive member penetrating through the turbine housing along a drive axis that is generally parallel to and transversely offset from the longitudinal axis about which the valve member rotates, and a drive arm attached to a distal end of the rotary drive member, a distal end of the drive arm engaging the valve member such that rotation of the rotary drive member about the drive axis causes the drive arm to rotate the valve member about the longitudinal axis, wherein the rotary drive member includes a lengthwise section having a substantially greater bending flexibility than that of a remainder of the rotary drive member; and a rotary actuator coupled to the rotary drive member and operable to rotatably drive the rotary drive member about the drive axis for rotating the valve member. a compressor including a compressor housing; a turbine housing defining at least part of a generally annular chamber extending circumferentially about a longitudinal axis of the turbine housing, the turbine housing defining a bore extending along the longitudinal axis; a turbine wheel disposed in the turbine housing; a nozzle passage leading from the chamber radially inwardly into the turbine wheel; the turbine housing defining an annular bypass volute surrounding the bore and arranged to allow exhaust gas to bypass the turbine wheel; an annular bypass valve disposed in the bypass volute, the bypass valve comprising a fixed annular valve seat and a rotary annular valve member, the valve member being disposed against the valve seat and being rotatable about the longitudinal axis for selectively varying a degree of alignment between respective orifices (73, 75) defined through each of the valve seat and valve member, ranging from no alignment defining a closed condition of the bypass valve, to at least partial alignment defining an open condition of the bypass valve; a rotary drive member penetrating through the turbine housing along a drive axis that is generally parallel to and transversely offset from the longitudinal axis about which the valve member rotates, and a drive arm attached to a distal end of the rotary drive member, a distal end of the drive arm engaging the valve member such that rotation of the rotary drive member about the drive axis causes the drive arm to rotate the valve member about the longitudinal axis, wherein the rotary drive member includes a lengthwise section having a substantially greater bending flexibility than that of a remainder of the rotary drive member; and a rotary actuator coupled to the rotary drive member and operable to rotatably drive the rotary drive member about the drive axis for rotating the valve member.