A drive unit (11, 111, 211) for a straddled vehicle which includes a vehicle body frame, a seat supported by the vehicle body frame, and the drive unit (11, 111, 211) provided below an upper end of an upper surface of the seat in a vehicle up-down direction and supported by the vehicle body frame, the drive unit (11, 111, 211) comprising: an engine main body unit including a crankshaft (S1, S101); a transmission unit including an input shaft rotationally driven by the crankshaft (S1, S101) and an output shaft rotationally driven by the input shaft; and a shared lubrication oil supply mechanism (22, 122, 222) including a first booster pump (80A, 180A, 280A) and a second booster pump (80B, 180B, 280B), the first booster pump (80A, 180A, 280A) being configured to pressurize shared lubrication oil by which both the engine main body unit and the transmission unit are lubricated, the second booster pump (80B, 180B, 280B) being driven by rotational force of one of rotational shafts of the engine main body unit and the transmission unit and configured to pressurize a part of the shared lubrication oil which has been pressurized by the first booster pump (80A, 180A, 280A) and has a pressure higher than atmospheric pressure, the shared lubrication oil supply mechanism (22, 122, 222) being configured to supply high-pressure shared lubrication oil, which is obtained by pressurizing, by the second booster pump (80B, 180B, 280B), the part of the shared lubrication oil having been pressurized by the first booster pump (80A, 180A, 280A) and having the pressure higher than atmospheric pressure, to at least one of the engine main body unit or the transmission unit, the shared lubrication oil supply mechanism (22, 122, 222) being configured to supply part of the shared lubrication oil having been pressurized by the first booster pump (80A, 180A, 280A) and having the pressure higher than atmospheric pressure to at least one of the engine main body unit or the transmission unit, without further pressurizing the shared lubrication oil by the second booster pump (80B, 180B, 280B). an engine main body unit including a crankshaft (S1, S101); a transmission unit including an input shaft rotationally driven by the crankshaft (S1, S101) and an output shaft rotationally driven by the input shaft; and a shared lubrication oil supply mechanism (22, 122, 222) including a first booster pump (80A, 180A, 280A) and a second booster pump (80B, 180B, 280B), the first booster pump (80A, 180A, 280A) being configured to pressurize shared lubrication oil by which both the engine main body unit and the transmission unit are lubricated, the second booster pump (80B, 180B, 280B) being driven by rotational force of one of rotational shafts of the engine main body unit and the transmission unit and configured to pressurize a part of the shared lubrication oil which has been pressurized by the first booster pump (80A, 180A, 280A) and has a pressure higher than atmospheric pressure, the shared lubrication oil supply mechanism (22, 122, 222) being configured to supply high-pressure shared lubrication oil, which is obtained by pressurizing, by the second booster pump (80B, 180B, 280B), the part of the shared lubrication oil having been pressurized by the first booster pump (80A, 180A, 280A) and having the pressure higher than atmospheric pressure, to at least one of the engine main body unit or the transmission unit, the shared lubrication oil supply mechanism (22, 122, 222) being configured to supply part of the shared lubrication oil having been pressurized by the first booster pump (80A, 180A, 280A) and having the pressure higher than atmospheric pressure to at least one of the engine main body unit or the transmission unit, without further pressurizing the shared lubrication oil by the second booster pump (80B, 180B, 280B).