We report on a technique for unidirectional operation of a ring laser with no intracavity elements other than the gain material. The Faraday effect in the gain medium combined with an out-of-plane Brewster-angled rod design produces an optical diode. Fabrication of the gain material as a prism permits a simple two-mirror ring-cavity arrangement. Single-frequency operation of a diode-pumped Nd:YAG laser based on this design is demonstrated. Using a 1-W diode pump, we achieved a single-frequency output of 190 mW at 1.064 microm.