The Chaîne de l'Épine, in the department of Savoie in southeast France, is a 20-kilometre (12 mi) long ridge of the Jura Mountains that runs north–south along the east side of the Lac d'Aiguebelette, from the Col de l'Épine west of Chambéry as far as the western edge of the Chartreuse Mountains, near the commune of Les Échelles.

Montbel built the Château de l'Épine on the ridge above Nances and placed the holy thorn relic in the castle's chapel.

The second explanation sees the Celtic god Pen as the source for both the name of the Chaîne de l'Épine ridge and the commune of Lépin-le-Lac to its west.

The Chaîne de l'Épine is an anticline, part of the "upper ridge" geological structure of the Jura Mountains.

[3] Situated between two Miocene molasse basins, the ridge is chiefly composed of limestones from the Jurassic and Cretaceous periods.

The portion south of the Col de Saint-Michel consists mainly of scree with a Jurassic limestone ridge.

[4] South of the Col de Saint-Michel pass, a change in the strike-slip fault deflects the ridge line to run northeast–southwest.

[5][6] The modern-day Route nationale 6 uses this tunnel to cross the southern end of the Chaîne de l'Épine ridge.