Lons-le-Saunier is a commune and capital of the Jura department in eastern France.
The town is in the heart of the Revermont region, at the foot of the first plateau of the Jura massif. The Jura escarpment extends to the east and south, while to the west lies the plain of Bresse and to the north extensive vineyards.
The River Vallière runs through the town, rising in a typical Jura blind valley not far away, at Revigny. It has been conduited since the 1960s on grounds of hygiene, since sewage outlets run into it. A small section remains in the open air near the parc des Bains, and only a single bridge (the pont de la Guiche) remains.
The town is approximately equally placed between Besançon, Dijon, Bourg-en-Bresse and Geneva, though the last of these lies on the other side of the Jura massif. It is served by the A39 autoroute, by which Dijon can be reached in about an hour and Lyon in an hour and a half. The town's railway station lies on the line from Strasbourg to Lyon.