Disclosed are thermal liners for protective garments and protective garments that comprise thermal liners. In one embodiment, a thermal liner comprises an insulation layer comprising a batt of entangled flame resistant fibers, the insulation layer having a three-dimensional pattern that defines a plurality of closed-cell air pockets that are configured to trap air to insulate a wearer of the thermal liner, the insulation layer being shaped and configured for inclusion in the protective garment and for donning by the wearer.