As the largest city in land area in the contiguous United States, Jacksonville is divided both formally and informally into a few large sections. Though most residents divide the city into Northside, Southside, Westside, and—increasingly over the past decade, Arlington—Jacksonville’s official website divides the city into six major sections:

• Greater Arlington, more commonly known to Jacksonville denizens simply as Arlington, is situated east and south of the St. Johns River and north of Beach Blvd.
• North Jacksonville is officially designated by the city website as everything north of the St. Johns & Trout Rivers and east of US 1. Much of this area is known by Jacksonville residents as the Northside, though much of what is called "Northside" does not fall within these boundaries, and much of what falls within these boundaries has not been traditionally known as "Northside".
• Northwest Jacksonville is located north of Interstate 10, south of the Trout River and surrounds the downtown section. The parts of this area between US Highway 1 and the Trout and St. John's River is usually considered part of either the "Northside" or, alternately, Downtown. Much of this section is actually rural land, not easily classified as part of any section.
• Southeast Jacksonville, almost universally known as Southside, refers to everything east of the St. Johns River and south of Beach Blvd.
• Southwest Jacksonville makes up most of what is known in Jacksonville as the Westside, though parts of Northwest Jacksonville also are considered part of the "Westside". It consists of everything west of the St. Johns River and south of Interstate 10.
• The Urban Core, most of which is commonly known as Downtown, includes the south & north banks of the narrowest part of the St. Johns River east from the Fuller Warren Bridge and extending roughly 4 miles north and east.

With the rapid growth in the eastern part of Duval County, the Intracoastal/Beaches/Ponte Vedra area is viewed by many as a major section as well, but is not generally included in a Jacksonville list since they lie outside of the Jacksonville city limits. There is also a distinct part of the city known as "Eastside" which those unfamiliar with Jacksonville's overall geography sometimes mistakenly regard as one of the major divisions of town, rather than the localized neighborhood which it is.

Today, what distinguishes a "section" of Jacksonville from a "neighborhood" is primarily a matter of size and divisibility. However, definitions are imprecise, and sometimes not universally agreed upon.

Each of these sections not only encompasses a large area, but also, each is divided into many neighborhoods. Each of these neighborhoods, in turn, has its own identity.

Each of these sections is divided into many neighborhoods. Some of these neighborhoods, such as Mandarin and LaVilla, had existed previously as independent towns or villages, prior to consolidation, and have their own histories.