  We suggest that the highest energy $ \gsim 10^{20}$ eV cosmic ray primaries
may be relativistic magnetic monopoles. Motivations for this hypothesis are
twofold: (i) conventional primaries are problematic, while monopoles are
naturally accelerated to $E \sim 10^{20}$ eV by galactic magnetic fields; (ii)
the observed highest energy cosmic ray flux is just below the Parker limit for
monopoles. By matching the cosmic monopole production mechanism to the observed
highest energy cosmic ray flux we estimate the monopole mass to be $\lsim
10^{10}$ GeV.
