List of ancient place names and geographical names / On

Latin name	Greek name	description	today	Sources and References	location
On		see Heliopolis
Onagrinum , Castellum Onagrinum		Roman fortress in Pannonia Inferior	Begeč in Serbia	Pleiades ;
Oncae				Smith ;
Onceium				Smith ;
Onchesm				Smith ;
Onchestus				Smith ;
Oneia				Smith ;
Oneum				Smith ;
Oningis				Smith ;
Onisia				Smith ;
Onoba aestuaria				Smith ;
Onobalas				Smith ;
Onobrisates				Smith ;
Onochonus				Smith ;
Onugnathus				Smith ;
Onuphis	Ὄνουφις  (Onouphis)	Place in the Nile Delta , capital of the Nomos Onouphites	Mahallat Minuf , 11 km north of Tanta , Egypt	Hdt. 2,166; Plin. Nat. 5.9 .; Smith ;