This study presents a mathematical analysis of the inﬂuence of non-ideal joint geometry on the temperature and residual stress distributions in circumferential welded joints. Manufacturing tolerances on component dimensions and thermal distortion during welding result in deviations from ideal joint geometry in virtually all welded joints. Although not problematic in many joint geometries, under the unique constraint conditions for circumferential welds, these deviations frequently exert an inﬂuence on the weld properties which can produce unacceptable weld defects. To limit the occurrence of such defects, there is a strong need for an improved understanding of the relationship between welding parameters, joint geometry, and the resulting temperature and residual stress distributions in circumferential joints. The fundamental results of this work can be applied by industrial welding practitioners in two clear and concrete ways: 1) with an understanding of the relative signiﬁcance of variations in welding parameters and geometry, it is possible to eliminate unnecessarily restrictive geometric tolerances and simply establish sufﬁcient requirements such that the process limitations will always govern joint quality; 2) identifying the mechanism (i.e. speciﬁc changes in the thermal and residual stress distribution) through which geometric variation leads to the occurrence of weld defects, allows for the development of tailored procedural techniques to counteract these effects and improve weld quality.