An engine unit includes an engine body, a crankshaft, and an oil tank. The engine body includes a cylinder unit and a crankcase. The crankshaft is accommodated in the crankcase and extends in the horizontal or substantially horizontal direction. The oil tank is located at a lateral portion of the engine body. The oil tank includes a tank body, a first component, and a second component. The first component is separate from the tank body and is joined to the tank body. The second component is separate from the tank body and is joined to the tank body. A first joint surface between the tank body and the first component extends in a direction different from that of a second joint surface between the tank body and the second component.