A rapid and decoupled three-degree-of-freedom trajectory planning approach is presented for maneuvering entry vehicles. A maneuver coefficient is defined to describe the lateral motion of a three-degree-of-freedom trajectory so that the designs for the longitudinal and lateral trajectories are decoupled. The longitudinal drag profile is planned according to the flight range that considers the maneuver coefficient. The lateral trajectory is controlled by an adjustable heading error corridor to achieve the required maneuver coefficient. The three-degree-of-freedom trajectory is finally generated based on the drag profile and the adjustable corridor. The trajectory planning algorithm is tested on two entry vehicles. Results indicate that this algorithm is capable of planning three-degree-of-freedom trajectories for nominal and maneuvering missions. The feasible region of the maneuver coefficient is investigated for each vehicle. The wide region demonstrates that the proposed planning algorithm is applicable and insensitive to estimation errors of the maneuver coefficient.