A main bearing housing for supporting a main rotor shaft of a wind turbine, wherein the main bearing housing defines a first end, a second end and a floor region intermediate the first and second ends. The main bearing housing comprises a first bearing arrangement positioned at the first end of the main bearing housing, a second bearing arrangement positioned at the second end of the main bearing housing, wherein the floor region includes a first oil sump positioned at the first bearing arrangement, and a second sump positioned at the second bearing arrangement. Advantageously, the embodiments of the invention provide that the bearings of the main bearing housing are lubricated by a lubrication system that includes sumps positioned at each of the fore and aft bearings of the main rotor shaft. The fore and aft bearings are therefore supplied with oil at suitable lubrication points and are part of the lubrication system that supplies oil to other components in the wind turbine that require oil lubrication, for example the gearbox and/or the generator bearings. The fore and aft bearings of the main bearing housing therefore do not require a separate lubrication system, such as a grease-based system and so the overall lubrication requirements for the nacelle are simplified.