Nassau County is the northeasternmost county of the U.S. state of Florida. According to the July 2022 United States Census analysis, the county's population was 97,899.

Florida's First Coast, or simply the First Coast, is a region of the U.S. state of Florida, located on the Atlantic coast of North Florida. The First Coast refers to the same general area as the directional region of Northeast Florida. It consists roughly of the counties abutting Jacksonville—Duval, Baker, Clay, Nassau, and St. Johns—and nearby Flagler County and Putnam County. The name originated in a marketing campaign in the 1980s, and has become part of Florida's regional vernacular.