An engine unit for a vehicle includes an engine body, an oil tank, and a power transmission shaft. The engine body includes a cylinder unit and a crankcase. The oil tank is disposed horizontally or substantially horizontally with respect to the engine body. The power transmission shaft includes a crankshaft supported by the crankcase. The power transmission shaft at least partially overlaps with the oil tank in a side view of the engine unit. The power transmission shaft extends from the engine body to a position beyond the oil tank in an axial direction of the crankshaft.