Lanester (French pronunciation: [lanɛstɛʁ]; Breton: Lannarstêr) is a commune in the Morbihan department in Brittany, in north-western France.

It is the largest suburb of the city of Lorient, across the river Scorff to the east.

Inhabitants of Lanester are called Lanestériens.

The mouth of the river Scorff separates the town of Lorient from the town of Lanester. Lanester is on the left bank while Lorient is on the right bank. The mouth of river Blavet forms a natural boundary to the east and to the south.

Lanester was created later than Lorient, with the development of shipyards on the left bank of the river Scorff in the middle of the nineteenth century. Lanester was created as a new commune in February 26, 1909. Before that, it came within the administrative area of the village of Caudan.

The old oil pier, located on the left bank of the Scorff, is due to be demolished in November 2025.

The municipality created a linguistic plan through Ya d'ar brezhoneg on 13 July 2006.

In 2008, 5.67% of the children attended the bilingual schools in primary education.