Abstract: A self-sealing flange assembly includes an elliptical shaped hole in a blind wall, the greatest diameter of which is larger than the smallest diameter of an elliptical shaped inner flange. Attached at a right angle to the surface of the flange is an internally or externally threaded nipple, bushing, stud or fastener. An annular groove located on the circumference of the flange contains a sealing means. At least one dimple at an apex of the elliptical flange locates the flange in situ when it is inserted through the wall opening and positioned thereon. An outer elliptical washer type element is tightened against the outer wall by rotation of a nut on the threads of the nipple, bushing, stud or rotating the bolt in the fastener, compressing the elliptical inner flange and sealing means against the inner wall forming a one piece leak proof assembly. The dimple used to locate the flange in situ also prevents rotation of the inner flange during the tightening process.