Château Phélan Ségur is a wine estate in the Saint-Estèphe region of the Médoc, northern Bordeaux. It was rated as Cru Bourgeois Exceptionnel in 2003, although this classification was later annulled amid legal wrangles. Regardless, Phélan Ségur is regarded as one of the better estates omitted from the 1855 Bordeaux Classification. The grand vin is typically composed of 50 to 65 percent Cabernet Sauvignon with the remainder made up from Merlot.

The estate lies just south of Saint-Estèphe village. Château Calon Ségur lies a short way north, towards the northern edge of the Saint-Estèphe appellation, while beyond Château Meyney, to the south, is the second growth Château Montrose.

In total, Phélan Ségur comprises 70 hectares (173 acres) of vines on the hillocks and plateaux of Saint-Estèphe, before the land drops away to the Canal de Calon waterway just beyond Calon Ségur.

Phélan Ségur's vineyards are divided into in four sections on clay and gravel soils, and are planted to about 58 percent Cabernet Sauvignon, 39 percent Merlot and 1.5 percent each of Cabernet Franc and Petit Verdot. The grapes are harvested manually and are initially sorted manually across vibrating sorting tables, before an advanced optical sorting machine makes the final selection.

Around 40 different tanks allow the fruit to be fermented according to the different vineyard parcels. The grand vin is aged for around 12 months in French oak barriques, with new wood never exceeding 50 percent.

The second wine, Frank Phélan, was created in 1986 and named after the son of the founder of the estate. It is sourced from around 15-hectares (37-acres) of old and young vines throughout the property.

The line-up is completed by La Croix Bonis, a Merlot-led cuvée intended for earlier drinking.

Phélan Ségur's history dates back to the late 18th Century, when Tipperary wine merchant Bernard O'Phelan arrived in Bordeaux. After marrying into the renowned Guestier family, he purchased the Saint-Estèphe properties Clos de Garramey and Ségur de Cabanac in 1805 and 1810, creating Château Ségur de Garramey, and built the Palladian chateau which remains there today.

The property took on its current name at the start of the 20th Century when it was changed from Château Ségur de Garramey to Château Phélan Ségur . Following a century of ownership by the Delon family of Léoville Las-Cases fame, Phélan-Ségur was acquired by Xavier Gardiner in 1984.

Gardiner (whose group owns the Lanson and Pommery Champagne houses) died in 2013 and the Phelan Segur estate was sold to Belgian shipping magnate and investor Philippe Van de Vyvere in 2017.