Gujan-Mestras (French pronunciation: [ɡyʒɑ̃ mɛstʁas]; Occitan: Gujan e Mestràs) is a commune in the Gironde department in southwestern France.

It is twinned with Santa María de Cayón, Spain Gujan-Mestras is located in the southern part of the Arcachon bay.

It is considered a major regional center for oyster farming, and is home to seven ports, which are from west to east:[5] Gujan-Mestras is surrounded by three communes.

It is west of Le Teich, east of La Teste-de-Buch and north of Sanguinet.

The city is otherwise served by lines 4 to 7 of the Baïa bus network, the local public transport system of the Arcachon Bay which links the Dune of Pilat to Facture-Biganos.