Puente Viesgo is a municipality in the Cantabria region of northern Spain. It lies inland in the Pas River valley, in the comarca of the same name, roughly 25 kilometres south-west of the regional capital, Santander.
The area is best known for the caves discovered near the town, which contain rock art and artefacts dating back to the Middle and Upper Palaeolithic. The most celebrated of these is the Cave of El Castillo, whose painted walls include some of the oldest known cave art in Europe, alongside the neighbouring caves of Las Monedas, La Pasiega and Las Chimeneas. Together they form the Monte Castillo cave complex, inscribed on the UNESCO World Heritage List in 2008 as part of the "Cave of Altamira and Palaeolithic Cave Art of Northern Spain" site.
The municipality also has a long-standing reputation as a spa town, centred on its hot mineral springs and the historic balneario by the river, which made it a popular resort in the nineteenth and early twentieth centuries. Its old quarter preserves traditional Cantabrian architecture, including the medieval Torre de los Bustamante and several stone mansions.