  We investigate the propagation of ultraheavy (UH) nuclei as ultrahigh-energy
cosmic rays (UHECRs). We show that their energy loss lengths at
$\lesssim300$~EeV are significantly longer than those of protons and
intermediate-mass nuclei, and that the highest-energy cosmic rays with energies
beyond $\sim100$ EeV, including the Amaterasu particle, may originate from such
UH-UHECRs. We derive constraints on the contribution of UH-UHECR sources, and
find that they are consistent with energy generation rate densities of UHECRs
from collapsars and neutron star mergers.
