Séglien (French pronunciation: [seɡlijɛ̃]; Breton: Seglian) is a commune in the Morbihan department of Brittany in north-western France.

[3] Inhabitants of Séglien are called in French Ségliennais.

Séglien is border by Silfiac to the north, by Langoëlan to the west, by Locmalo and Guern to the south and by Malguénac and Cléguérec to the east.

From the Roman period there remains a section of the Roman road connecting Castennec to Carhaix, passing through Mané-Guégan, Quénécalec and Resterhierven.

On this road, not far from Saint-Germain, there is a mutilated cylindrical stone, which could have been a milestone.