Neptune Beach is a beachfront city east of Jacksonville in Duval County, Florida, United States. When the majority of Duval County communiti…Neptune Beach is a beachfront city east of Jacksonville in Duval County, Florida, United States. When the majority of Duval County communities consolidated with Jacksonville in 1968, Neptune Beach, along with Jacksonville Beach, Atlantic Beach and Baldwin remained quasi-independent. Like those other municipalities, it maintains its own municipal government but its residents vote in the Jacksonville mayoral election and are represented on the Jacksonville city council. As of the 2020 census, the population is 7,217, up from 7,037 at the 2010 census. Neptune Beach is the smallest of the Jacksonville Beaches communities. it is part of the Jacksonville, Florida Metropolitan Statistical Area.