Various embodiments of restraint harnesses for use in land, air, and sea vehicles are described herein. In one embodiment, for example, a restraint harness can include a first shoulder web, a second shoulder web, and a torso web. A first end portion of the torso web can include a buckle that is configured to engage a connector at a second, opposite end portion of the torso web. The restraint harness can further include first and second portions of a stiffening material attached to first and second portions of the first and second shoulder webs, respectively. The stiffening material can form the first and second shoulder webs into preformed openings with inverted U-like shapes.