Clamp for joining two metal pipes, particularly of the type constituting the exhaust system of a vehicle engine, the ends in facing relationship of the two tubes to be joined having conical shape complementary bearing surfaces which project with respect to the cylindrical outer surface of the pipes. The clamp is constituted by an open ring of inverted V-shaped cross-section, the two ends of which ring comprise bearing elements for means provided for tightening and holding the ring in its closed position when the clamp has been placed over the pipes to be joined.