Described herein are various protective helmets, including helmets designed for equestrian use. In one embodiment, an equestrian helmet (1) includes a front shell (2) and a rear shell (3). Shell (3) is moveable with respect to shell (1) to provide the helmet with two configurations. The first of these is an open configuration where the helmet is configured for receiving within the helmet or removing from the helmet a human head (4). The second configuration is a closed where shell (3) is releasably lockingly engaged to shell (2) for securely containing head (4) within helmet (1).