A stent graft (20) has a tubular body of graft material (21), a number of self expanding stents (67) associated with the tubular body to define a fluid flow path through the stent graft when the self expanding stents are in their expanded configurations. At least one fenestration (22) in the tubular body is adapted to receive a side arm stent graft (71) to provide a fluid flow path from the tubular body and through the side arm stent graft. The or each fenestration has at least an inner ring (26) and an outer ring (24) and graft material (28) extending from the inner ring to the outer ring and the outer ring being in the tubular body of graft material. The inner ring can be hinged (31) to the outer ring or concentric within the outer ring. An intermediate ring (86) may also be used between the inner and outer rings.