San Marco in Lamis is a town and comune located in the province of Foggia within the Apulia region of southeast Italy. It is situated in the Gargano massif area, specifically inside the Parco Nazionale del Gargano, and belongs to the Comunità Montana del Gargano.
The town's territory is traversed by part of the Via Sacra Langobardorum. Notable landmarks within the municipality include the Santuario di Santa Maria di Stignano and the Convento di San Matteo apostolo. The Santuario di Santa Maria di Stignano is associated with the ruins of Castelpagano Castle, which overlooks a slope in the territory of Apricena.