This paper investigates the attitude control problem for a horizontal takeoff and horizontal landing reusable launch vehicle (HTHLRLV). A predefined-time attitude tracking controller is proposed for the HTHLRLV. Firstly, the dynamics model of the HTHLRLV is established and the state equation for the attitude tracking error is derived. Subsequently, a novel sliding mode surface with predefined-time stability is designed. To compensate for external disturbances or model uncertainties, a predefined-time disturbance observer is developed, which simplifies the controller complexity and addresses the singularity issue arising from the differentiation of the sliding mode surface. Furthermore, leveraging the proposed sliding mode surface and disturbance observer, a predefined-time controller is derived. Finally, numerical simulations are conducted to validate the effectiveness and superiority of the proposed controller.