Onyx Cave may refer to several things in the United States:
Onyx Cave (Arizona), a National Natural Landmark Onyx Cave (Arkansas), a small show cave Onyx Cave (Kentucky), a show cave Great Onyx Cave, Kentucky Great Onyx Cave Entrance, Mammoth Cave, Kentucky, listed on the NRHP in Kentucky Crystal Onyx Cave, Kentucky Onyx Cave (Newburg, Missouri), listed on the NRHP in Missouri Onyx Mountain Caverns, Missouri
See also Cave onyx