The U.S. state of Connecticut is divided into two numbering plan areas, each configured as an overlay complex of two area codes each.
| Area code | Year created | Parent NPA | Overlay | Numbering plan area |
|---|---|---|---|---|
| 203 | 1947 | – | 203/475 | Southwestern Connecticut (Fairfield County (except for Sherman); New Haven County, and the towns of Bethlehem, Woodbury, as well as a small part of Roxbury in Litchfield County) |
| 475 | 2009 | 203 | ||
| 860 | 1995 | 203 | 860/959 | Northern and eastern Connecticut |
| 959 | 2014 | 860 | ||