Faxaflói (Icelandic pronunciation: [ˈfaxsaˌflou.ɪ]), formerly known in English as Faxa Bay and Faxe Bay, is a bay in Southwest-Iceland between the peninsulas of Snæfellsnes and Reykjanes.

The capital of the island, Reykjavík, is situated on its southern shore. From Reykjavik it is possible to see the peninsula of Akranes in the north-east and even the Snæfellsjökull at a distance of about 120 km (75 mi).

Faxaflói has always been a source of nourishment of the people living on its shore. In former times, fishermen went out in small boats to fish near the shore. Today the ships are much bigger, but have to go farther out to sea if they wish to catch fish.

Just north of Reykjavík in Kollafjörður is the small island Viðey. It has been inhabited since 1943 but a former settlement has been proven from the 10th century onwards. During the 12th century a chapel was constructed, and a monastery was founded in 1225, existing till the final assertion of Reformation by the end of the 16th century. The island and the remains of the settlement can be visited by taking a ferry from Reykjavík harbour.