Tensioning apparatuses for occupant restraint systems and associated systems and methods. In one embodiment, an occupant restraint system for a vehicle can include a flexible web configured to extend across at least a portion of an occupant seated in the vehicle and an electrically actuated web retractor operably coupled to a proximal end portion of the web. The web retractor is configured to automatically wind and unwind the web. The system also includes an acceleration sensor operably coupled to the electrically actuated web retractor. The acceleration sensor is configured to send an electrical signal to the web retractor in response to a vehicle acceleration above a preset magnitude. In response to the signal, the web retractor is configured to (a) retract the web, and/or (b) at least temporarily prevent the web from moving inwardly or outwardly.