I'm not sure, he works in a different office than I do. As far as I know, he's American, and I'm not sure if he had a mononym from birth, or if he changed his name.
The other famous one is Burma - U Thant, third Secretary-General of the United Nations, was actually just called Thant, but nobody could handle that in 1961, so they stuck the Burmese version of 'Mr' on the front to make something they could recognise as a name.