Deep erosional level, rich exposure and excellent preservation of parts of the passive margin make the Arctic Scandinavian Caledonides (north of 66°N) an ideal area for attempting a reconstruction of the pre-collisional continental margin of a collisional mountain belt. Such a reconstruction is essential for the safe identification of suspect and exotic terranes, but also because “passive” margins seem to partly control tectonics and metamorphism throughout the evolution of mountain belts. The palinspastic reconstruction of the Baltoscandian Margin attempted in this paper suggests that all thrust sheets in the Arctic Scandinavian Caledonides below the nappes of ensimatic affinity could derive from a northern extension of the Caledonide foreland of southwestern Scandinavia. Thus, the paper calls in question recent interpretations of principal units of the Arctic Scandinavian Caledonides (e.g., the Kalak Nappe Complex, including the Sørøy Group type stratigraphy) as exotic terranes, and the sedimentary detritus of the Sørøy Group as foreign to the Baltoscandian Margin. The varied evidence of magmatism of rift affinity found in many nappes and in the southern foreland is reviewed and interpreted in terms of a coherent, though protracted evolution from the ca. 900 Ma, high-Ti-K-P-LREE continental tholeiites of the foreland aulacogen to the ca. 580 Ma T-MORB sheeted dykes of the outermost continental margin. This evolution is compared to that of modern rifts (Afro-Arabian rift system); such comparison allows interpretation of the renowned Seiland Igneous Province as magmatism in a mid-crustal section of the Baltoscandian Margin. The evidence of a strong MORB affinity of mafic dykes occurring in most thrust sheets below the exotic terranes requires extensive thinning of a wide zone of the continental margin prior to the ultimate break-up. The paper summarizes unambiguous evidence that the rifted and dyke-intruded margin was depressed to at least 50 km depth and imbricated and uplifted in Late Cambrian-Early Ordovician times, and the concept of a Finnmarkian event is retained for this early diastrophism affecting the Baltoscandian Margin. A remarkable feature of the Arctic Scandinavian Caledonides is the evidence that the sheeted-dyke complex must have been detached from the diving margin at an early stage and carried towards the foreland, thus escaping high-pressure metamorphism at 505-500 Ma. Finnmarkian cooling ages of thrusts within the Seve Nappe Complex are in conflict with popular flat-ramp models of Silurian-Early Devonian (Scandian) thrusting developed for this nappe complex. Rich evidence of metamorphic and isotopic disequilibrium in the nappe stack of the Arctic Scandinavian Caledonides suggests that the perturbations of the geotherm caused by early understacking of cold continental crust never recovered before renewed crustal thickening during Scandian accretion of exotic terranes and final assembly of the mountain belt. This raises questions about the actual significance of results obtained by P- T- t modelling in other overthrust belts, where such evidence is not preserved.