Is a sleeping mat required for the Camino de Santiago?
If you plan to stay every night in an albergue or hostel, don't take a mat with you, you will sleep in a normal bed or on a mattress. Many pilgrims bring mat to the Camino but after some stages they just throw it away or leave it in the albergues, so if you really need one, you can get one for free anywhere. The only reason when you need a mat is sleeping in a tent.
Nothing unnecessary just exactly what you need for your Camino