The Aguadilla-Isabela-San Sebastián Metropolitan Statistical Area is a United States Census Bureau defined Metropolitan Statistical Area (MSA) in northwestern Puerto Rico. A July 1, 2009 Census Bureau estimate placed the population at 342,495, a 9.56% increase over the 2000 census figure of 312,602.
Aguadilla-Isabela-San Sebastián is the second largest metropolitan area (by population) in Puerto Rico after San Juan–Caguas–Guaynabo and is the fastest growing MSA in the Commonwealth.
A total of eight municipalities (Spanish: municipios) are included as part of the Aguadilla-Isabela-San Sebastián Metropolitan Statistical Area. They are: