The GR10 is the French Pyrenees thru-hike, ranging from the Atlantic Ocean (in Hendaye) to the Mediterranean Sea (in Banyuls-sur-Mer). The GR10 comfortably sits in between the HRP trail that stays up in the mountain and the valley. But do not underestimate the trail, as while it does not go so high on the Pyrenees ridge (maximum 2753m), it piles up a massive denivelation often descending low in the valley.
Numerous train stations and bus stations are scattered along the GR10, making it easy to access for a complete thru-hike or a section hike.