| Essonne | |
| Map: | Essonne.png |
| Name Etymology: | Latin Exona or Axonia, from the Celtic water goddess Acionna[1] |
| Source1 Location: | Gâtinais |
| Mouth Location: | Seine |
| Mouth Coordinates: | 48.6144°N 2.4811°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | France |
| Length: | 101km (63miles) |
The Essonne (in French pronounced as /ɛsɔn/) is a 101km (63miles) long French river. It is a left tributary of the Seine. Its course crosses the departments of Loiret and Essonne, and it gives its name to the latter. The Essone's name and the present name of its higher course (the Œuf) originate in Acionna, a Gallo-Roman river goddess attested at Orléans (Genabum).
It begins on the Gâtinais plateau at La Neuville-sur-Essonne through the confluence of two rivers, the Œuf—whose source is near Chilleurs-aux-Bois, Loiret, at 130m (430feet) above sea level—and the Rimarde—whose source is near Nibelle, Loiret, 182m (597feet). Notably it runs through Malesherbes and La Ferté-Alais, before running into the Seine at Corbeil-Essonnes.
Notable among the Essonne's tributaries is the Juine, 53km (33miles) long, which enters from the left. The other tributaries are short streams (the Velvette, the Ru de D’Huison, the Ru de Misery off the left bank; Ru de Boigny and the Ru de Ballancourt off the right bank).
From Corbeil-Essonnes to its terminus at Malesherbes, the RER D runs along the valley of the Essonne. Part of the basin feeding the Essonne, as well as its course between Malesherbes and La Ferté-Alais, are in the parc naturel régional du Gâtinais français.
The Essonne runs through the communes of: