Background and Aims: Based on parentage analysis of a large nuclear simple sequence repeat (SSR) marker database of grapevine genotypes, we propose the pedigree of several cultivars from southwestern France including Merlot, one of the world's major black winegrapes.Methods and Results: The putative mother of Merlot, deduced from inheritance at 55 nuclear and three chloroplast microsatellite loci, is a non-referenced and previously unknown cultivar, first sampled some years ago in northern Brittany where vines were cultivated at the end of the Middle Ages, and then identified in four places in Charentes. Considering both the name used by the growers of this grape and the literature, we have named it Magdeleine Noire des Charentes. The putative father of Merlot is Cabernet Franc, already involved in the parentage of Cabernet-Sauvignon. Further analysis of genetic relationships leads us to propose the kinship group of Merlot composed, among others, of Carmenere (Gros Cabernet x Cabernet Franc), Merlot Blanc (Merlot x Folle Blanche), Cot (Magdeleine Noire des Charentes Prunelard) and Mourtes (Magdeleine Noire des Charentes x Penouille).Conclusions: These results shed new light on the origin of Merlot and on the relationships among several cultivars from southwestern France.Significance of the Study: Our discovery of the key genetic role of a previously unknown cultivar in the origins of some significant cultivars reinforces the importance of deep exploration, before it is too late, to discover original genotypes which have not yet been collected or referenced