This paper focuses on the development of a lightweight, composite floating crew floor designed to withstand the severe loading requirements of an underbody blast. Energy absorbing devices decouple the floor from the surrounding vehicle structure; therefore, in the event of an underbody blast, the impulse is spread out over a longer period of time, thus reducing the loads into the floor where the crew seats are attached. The composite floor development included: characterizing candidate materials for structural and flame/smoke/toxicity characteristics, design optimization of the composite floor geometry, modeling the response of the floor assembly during a simulated underbody blast event, and manufacturing of a physical composite crew floor. Based on this effort, the composite floor was able to meet the structural requirements of the underbody blast event, while reducing weight by more than 55% compared to the baseline aluminum floor. Moreover, due to the significant reduction in mass and efficient design, the raw material cost of the composite floor was approximately cost neutral compared to the baseline aluminum floor that was machined from solid aluminum billet.