By introducing field line potentials for the magnetic induction and current line potentials for the current density, it is shown that the equations which describe a static equilibrium system, in the ideally conducting magnetohydrodynamic approximation, may be derived from two equivalent variational principles. The problem of integration is essentially that of finding a transformation of the potentials which changes one of the associated Lagrangian functions into the other. The assumption that the current density has no component in one direction of a rectangular Cartesian coordinate system leads to a new class of fully three dimensional equilibria having a plane symmetry.