The Clarence is a river in northern France whose 33-kilometre (21 mi) course crosses the department of Pas-de-Calais.

Its source is near the village of Sains-lès-Pernes. It flows through the communes of Sachin, Pernes, Calonne-Ricouart, Calonne-sur-la-Lys and Gonnehem, finally joining the Lys near Merville.

It has two tributaries, the Nave and the Grand Nocq.