The disclosure relates to thermally reversibly crosslinked polyolefins (TRC-PO) and methods for making the same. A TRC-PO can be formed by reactive melt-processing a mixture including (i) a polyolefin, (ii) an initiator, and (iii) a reversible crosslinker. The reversible crosslinker includes (A) a grafting agent moiety selected from unsaturated cyclic anhydrides, unsaturated cyclic imides, cyclic nitroxides, and ring-opened analogs thereof, and (B) a crosslinking moiety bound to the cyclic grafting agent moiety. This reactive melt-processing, for example including reactive extrusion, forms a thermally reversibly crosslinked (TRC) polyolefin with polyolefin chains reversibly crosslinked via the reversible crosslinkers, which provide dynamic covalent bonds, such as siloxanes and esters, that are amenable to melt re-processing to re-from or otherwise re-use the TRC-PO while still retaining the reversible crosslinks after re-processing. Catalysts and additives such as rheology modifiers can be added to the melt-processing mixture.