  A closed superconducting circuit containing an odd number of $\pi$-junctions,
a $\pi$-ring, has a finite current in the ground state. We explicitly construct
such rings for d-wave superconductors and demonstrate the existence of
spontaneous currents by direct self-consistent solutions to the Bogoliubov de
Gennes equations. We show that the current has a topological origin due to the
frustration of the d-wave order parameter, which is only partially explained by
the Sigrist-Rice tunneling formula.
