A clamping collar comprising: a belt having two free ends, at least one of said free ends being curved back to form a loop, said loop being defined by an outer belt portion and by an underlying inner belt portion; and a tightening system suitable for co-operating with said loop so as to tighten said belt; in which clamping collar said outer belt portion presents a pushed-in portion, set back relative to the outer outline of the loop, which pushed-in portion defines a tightening wall with which the tightening system comes into engagement, and is flanked on either side by respective ones of two edge segments of the outer belt portion.