Ornain

{{Infobox river

| name = Ornain

| image = Bar-le-Duc pont Notre-Dame.jpg

| image_caption = Ornain flowing through Bar-le-Duc

| map = Ornain.png

| source1_location =

| mouth_location = Saulx

| mouth_coordinates = {{coord|48|46|7|N|4|48|15|E|format=dms|display=inline,title}}

| progression = {{RSaulx}}

| subdivision_type1 = Country

| subdivision_name1 = France

| length = {{convert|116|km|abbr=on}}

| source1_elevation =

| discharge1_avg =

| basin_size =

}}

The Ornain ({{IPA|fr|ɔʁnɛ̃}}) is a 116 km long river in northeastern France, right tributary of the Saulx (Seine basin).{{sandre|id=F56-0400|nom=L'Ornain}} It is formed near the village Gondrecourt-le-Château by the confluence of the small rivers Ognon and Maldite. It flows generally northwest. Its course crosses the following départements and towns:

• Meuse: Gondrecourt-le-Château, Ligny-en-Barrois, Bar-le-Duc, Revigny-sur-Ornain
• Marne

The Ornain flows into the Saulx in Pargny-sur-Saulx. The part of the Marne-Rhine Canal between Demange-aux-Eaux and Sermaize-les-Bains runs parallel to the Ornain.