* The Greater One-Horned Rhino: These rhinos live in India's Assam state, specifically in the Kaziranga National Park, Manas National Park, and Pobitora Wildlife Sanctuary. They are also found in other protected areas in the state.
* The Javan Rhino: These rhinos are critically endangered and live in Ujung Kulon National Park in Java, Indonesia.
So, depending on which one-horned rhino you're asking about, the answer is either India or Indonesia.