Château Phélan Ségur lies in the commune of Saint-Estèphe in the Bordeaux region of France, neighbouring vineyards Château Calon-Ségur and Château Montrose. In a 2003 Cru Bourgeois classification revision, it was listed as one of 9 Cru Bourgeois Exceptionnels.
A second wine is produced since 1986, under the label Frank Phelan. A more recent venture is a wine titled La Croix Bonis.
The Irishman Bernard Phelan (1770-1841) acquired the Domaine Le Clos de Garamey in 1805 and Ségur de Cabarnac in 1810. In Ireland, he was a neighbour and friend of Hugh Barton who established Château Léoville-Barton. By his death in 1841 the estate combined to form Château Ségur de Garamey, which passed on to his son Frank Phelan, 30 years a mayor of Saint-Estèphe.
The current owner since 1985 is Xavier Gardinier, with sons Thierry, Stéphane and Laurent. Michel Rolland is employed as a consulting enologist.
The vineyard area extends 89 hectares or 220 acres. The grape varieties used are 50% Merlot, 45% Cabernet Sauvignon, 4% Cabernet Franc, and 1% Petit Verdot.