In Quebec, civil union is a disposition that provides a legal framework for a conjugal relationship, the essential elements of which are implicit within the text of the Civil Code of Québec. The common-law Canadian provinces, on the other hand, cover this alternative to marriage explicitly, in laws directed at "domestic" or family relations. In France, the Civil Solidarity Pact and even concubinage are covered by the Civil Code. The Quebec approach is an original one. We will be explain it by demonstrating that civil union, as it currently exists in Quebec law, is very similar to marriage as it was practised in Roman law in classical times. Our analysis leads us to suggest that Quebec has reinvented or rediscovered the Roman marriage of the classical epoch, via the civil union as practised in this province. It also allows us to suggest that the "Quebec-style civil union" offers a possibly more coherent structure than our current form of marriage.