  In this paper, we introduce PoMiN, a lightweight $N$-body code based on the
post-Minkowskian $N$-body Hamiltonian of Ledvinka et. al., which includes
general relativistic effects up to first order in Newton's constant $G$, and
all orders in the speed of light $c$. PoMiN is written in C and uses a
fourth-order Runge-Kutta integration scheme. PoMiN has also been written to
handle an arbitrary number of particles (both massive and massless), with a
computational complexity that scales as $O(N^2)$. We describe the methods we
used to simplify and organize the Hamiltonian, and the tests we performed
(convergence, conservation, and analytical comparison tests) to validate the
code.
