This volume of the series gives an overview on Rigid Polymer Networks written by two reputed experts in the field. A broad range of densely-branched, highly-crosslinked aromatic networks and gels of increasing rigidity are discussed, with special emphasis on aromatic rigid liquid-crystal polymer networks. The synthetic procedures to create the networks are briefly described and extensively referenced. Features of one-step and two-step rigid networks in their pre-gel and post-gel states are discussed. Some first steps are then taken in the theoretical treatment of LCP networks with long aromatic segments of decreasing stiffness. The current state of theory dealing with the broader class of highly-crosslinked rigid aromatic networks and gels is finally mentioned.