The Falleron is 52 km long,[1] from its source at an altitude of 60 metres (200 ft), in the town of Grand'Landes in the Vendée department flowing west to its mouth in the Bay of Bourgneuf at the Port du Collet [fr].

[5] At Saint-Etienne-de-Mer-Morte the ruisseau de la Blanchardière (9 km (5.6 mi) joins on the left bank and defines a further section of the departmental boundary.

A pumping station at La Pommeraie, built in 1962, raises water the remaining 3 metres (9.8 ft) from the Tenu to the Falleron.

[11] Downstream of Machecoul the Falleron opens into the marshes and polders of the Marais Breton, and divides and connects with a complex network of freshwater and semi-tidal creeks and canals.

Further downstream the Dain canal joins on the left bank and flows 15 km (9.3 mi) south-west around the former isle and town of Bouin reaching the Bay of Bourgneuf at L'Epoids.