an arrondissement in the department of the Upper Rhine, in France. The extent is 444 square miles, or 284,160 acres, and it contains seven cantons and 106 communes, with 99,013 inhabitants. The chief city of the arrondissement is of the same name, and is situated on a hill, whose base is washed by the river Ill, about two leagues from Mulhausen. It has 2400 inhabitants. Long. 7. 11. E. Lat. 47. 7. N.