  Including world-sheet orientation-reversing automorphisms in the orbifold
program, we recently reported the twisted operator algebra and twisted KZ
equations in each open-string sector of the general WZW orientation orbifold.
In this paper we work out the corresponding classical description of these
sectors, including the {\it WZW orientation-orbifold action} -- which is
naturally defined on the solid half cylinder -- and its associated WZW
orientation-orbifold branes. As a generalization, we also obtain the {\it
sigma-model orientation-orbifold action}, which describes a much larger class
of open-string orientation-orbifold sectors. As special cases, this class
includes twisted open-string {\it free boson} examples, the open-string WZW
sectors above and the open-string sectors of the {\it general coset orientation
orbifold}. Finally, we derive the {\it orientation- orbifold Einstein
equations}, in terms of twisted Einstein tensors -- which hold when the twisted
open-string sigma-model sectors are 1-loop conformal.
