Following the set up of the scientific program coordinated by the French National Centre for Scientific Research after the fire of the 15th April 2019, the clearing, sorting and inventory of the remains of Notre-Dame de Paris revealed a great diversity of iron alloys within the cathedral. The study of these metals allows enriching our knowledge of the monument but can also reveal social practices and their evolution according to the different periods of the building site. On seeing the cathedral architecture as a materialization of the social life around the construction yard, the archaeometallurgical analyses of the iron armatures can provide information on the production and circulation of the metal, the manufacturing processes or their role in the structure of the building, along with the dating of the material. Among iron artefacts in the cathedral are found staples in the masonry of the tribunes, nave, aisles and upper walls. The restoration works also reveal various tie-rods, dowels, ridge caps and framing irons such as nails, bolted rods or keyed dowels. The shaping of 28 of these ferrous armatures and the quality of the metal production has been highlighted by metallographic analyses. Artefacts with sufficiently high carbon content were also radiocarbon dated, revealing the different construction and repair campaigns of the cathedral. Slag inclusions were analyzed by SEM-EDS (major elements) to study the iron manufacturing processes and by LA-ICP-MS (trace elements) to look for iron provenance. Trace element composition of slags from 9 archaeological iron production sites in Île-de-France was also determined by ICP-MS. The comparison with the composition slag inclusions of the metal reinforcements enables to propose provenance hypotheses for the supply of Notre-Dame’s building yard. These archaeometallurgical studies show a great diversity of provenances and renew our understanding of iron circulation and trade in medieval Paris.