Fjarðabyggð is a municipality located in eastern Iceland, in the Eastern Region.

The municipality was formed in 1998 with the union of the former municipalities of Eskifjörður, Neskaupstaður and Reyðarfjörður. Austurbyggð, Fáskrúðsfjarðarhreppur and Mjóafjarðarhreppur were merged into Fjarðabyggð in 2006, and Breiðdalshreppur merged in 2018.