Which grape variety is the only red grape permitted in the northern Rhone?

The only red grape variety permitted in the northern Rhône is Syrah. This region is renowned for its high-quality red wines, and Syrah is the dominant variety throughout the northern Rhône appellations, including Côte-Rôtie, Hermitage, and St-Joseph. Syrah thrives in the region's steep, rocky slopes, producing wines that are rich, full-bodied, and complex with flavors ranging from dark fruit to spices and sometimes floral notes.

Other varieties mentioned, such as Grenache and Mourvèdre, are indeed critical in the southern Rhône, where they contribute significantly to famous blends like Châteauneuf-du-Pape. However, they are not authorized in the northern Rhône for red wine production. While Cinsault is also important in the southern Rhône, especially in blended wines, it is not cultivated in the northern Rhône. This clear distinction in grape varieties reflects the unique terroir and winemaking traditions of the northern Rhône Valley, where Syrah stands as the iconic red grape.