| County | FIPS code | County seat | Est. | Formed from | Etymology | Density | Population | Area | Map |
| Alachua County | 001 | Gainesville | 1824 | Duval and St. Johns | From a Seminole-Creek word meaning "jug", apparently in reference to the sinkholes common in the area | 333.85 | 291,782 | 874 sq mi(2,264 km2) | |
| Baker County | 003 | Macclenny | 1861 | New River | James McNair Baker (1821–1892), a Confederate senator and later a judge in the fourth judicial district | 50.13 | 29,325 | 585 sq mi(1,515 km2) | |
| Bay County | 005 | Panama City | 1913 | Calhoun and Washington | St. Andrew's Bay, the central geographic feature of the county | 261.41 | 199,718 | 764 sq mi(1,979 km2) | |
| Bradford County | 007 | Starke | 1858 | Columbianamed New River until 1861 | Richard Bradford, the first officer from Florida to die in the Civil War; he was killed during the Battle of Santa Rosa Island | 95.82 | 28,075 | 293 sq mi(759 km2) | |
| Brevard County | 009 | Titusville | 1844 | Hillsborough and Mosquitonamed St. Lucie until 1855 | Theodore Washington Brevard, early settler and later state comptroller from 1853 to 1861 | 646.80 | 658,447 | 1,018 sq mi(2,637 km2) | |
| Broward County | 011 | Fort Lauderdale | 1915 | Miami-Dade and Palm Beach | Napoleon Bonaparte Broward (1857–1910), 19th governor of Florida from 1905 to 1909 | 1685.25 | 2,037,472 | 1,209 sq mi(3,131 km2) | |
| Calhoun County | 013 | Blountstown | 1838 | Franklin, Jackson, and Washington | John C. Calhoun (1782–1850) leading Southern politician from South Carolina | 23.42 | 13,278 | 567 sq mi(1,469 km2) | |
| Charlotte County | 015 | Punta Gorda | 1921 | DeSoto | Probably a corruption of the name of the Calusa, a group of Native Americans from the area | 305.65 | 212,122 | 694 sq mi(1,797 km2) | |
| Citrus County | 017 | Inverness | 1887 | Hernando | The county's citrus trees | 291.39 | 170,174 | 584 sq mi(1,513 km2) | |
| Clay County | 019 | Green Cove Springs | 1858 | Duval | Henry Clay (1777–1852), Secretary of State from 1825 to 1829 under John Quincy Adams | 393.94 | 236,760 | 601 sq mi(1,557 km2) | |
| Collier County | 021 | East Naples | 1923 | Lee | Barron Collier (1873–1939), an advertising entrepreneur who developed much of the land in southern Florida | 205.45 | 416,233 | 2,026 sq mi(5,247 km2) | |
| Columbia County | 023 | Lake City | 1832 | Alachua | Christopher Columbus (c. 1451–1506), explorer of the Americas | 92.82 | 73,977 | 797 sq mi(2,064 km2) | |
| DeSoto County | 027 | Arcadia | 1887 | Manatee | Hernando de Soto (c. 1496/1497–1542), a Spanish explorer and conquistador | 57.68 | 36,744 | 637 sq mi(1,650 km2) | |
| Dixie County | 029 | Cross City | 1921 | Lafayette | Dixie, the common nickname for the Southern United States | 25.02 | 17,614 | 704 sq mi(1,823 km2) | |
| Duval County | 031 | Jacksonville | 1822 | St. Johns | William Pope Duval (1784–1854), the first governor of the Florida Territory | 1363.25 | 1,055,159 | 774 sq mi(2,005 km2) | |
| Escambia County | 033 | Pensacola | 1821 | One of the two original counties | Disputed origin; possibly from the Creek or Choctawword Shambia, meaning "clear water", or from Spanish word "cambiar", meaning to barter | 498.91 | 331,275 | 664 sq mi(1,720 km2) | |
| Flagler County | 035 | Bunnell | 1917 | St. Johns and Volusia | Henry Morrison Flagler (1830–1913), founder of the Florida East Coast Railway | 281.95 | 136,744 | 485 sq mi(1,256 km2) | |
| Franklin County | 037 | Apalachicola | 1832 | Gadsden and Washington | Benjamin Franklin (1706–1790), one of the Founding Fathers of the United States of America | 24.31 | 12,979 | 534 sq mi(1,383 km2) | |
| Gadsden County | 039 | Quincy | 1823 | Jackson | James Gadsden (1788–1858), American diplomat and namesake of the Gadsden Purchase | 85.56 | 44,151 | 516 sq mi(1,336 km2) | |
| Gilchrist County | 041 | Trenton | 1925 | Alachua | Albert W. Gilchrist (1858–1926), the 20th governor of Florida | 57.97 | 20,233 | 349 sq mi(904 km2) | |
| Glades County | 043 | Moore Haven | 1921 | DeSoto | The Florida Everglades | 16.97 | 13,132 | 774 sq mi(2,005 km2) | |
| Gulf County | 045 | Port St. Joe | 1925 | Calhoun | The Gulf of Mexico | 28.10 | 15,876 | 565 sq mi(1,463 km2) | |
| Hamilton County | 047 | Jasper | 1827 | Jefferson | Alexander Hamilton (1757–1804), the first United States Secretary of the Treasury and a Founding Father | 27.83 | 14,334 | 515 sq mi(1,334 km2) | |
| Hardee County | 049 | Wauchula | 1921 | DeSoto | Cary A. Hardee (1876–1957), governor of Florida at the time of creation of Hardee County | 40.92 | 26,068 | 637 sq mi(1,650 km2) | |
| Hendry County | 051 | LaBelle | 1923 | Lee | Francis A. Hendry (1833–1917), early Floridian pioneer and politician | 40.01 | 46,130 | 1,153 sq mi(2,986 km2) | |
| Hernando County | 053 | Brooksville | 1843 | Alachua and Hillsboroughnamed Benton from 1844 to 1850 | Hernando de Soto (c. 1496/1497–1542), a Spanish explorer and conquistador | 456.38 | 218,150 | 478 sq mi(1,238 km2) | |
| Highlands County | 055 | Sebring | 1921 | DeSoto | Named for the county's hilly terrain | 106.79 | 109,778 | 1,028 sq mi(2,663 km2) | |
| Hillsborough County | 057 | Tampa | 1834 | Alachua | Wills Hill, Earl of Hillsborough (1718–1793), former Secretary of State for the Colonies | 1504.69 | 1,581,426 | 1,051 sq mi(2,722 km2) | |
| Holmes County | 059 | Bonifay | 1848 | Jackson and Walton | Holmes Creek, which forms the eastern boundary of the county | 41.24 | 19,876 | 482 sq mi(1,248 km2) | |
| Indian River County | 061 | Vero Beach | 1925 | St. Lucie | The Indian River Lagoon, which flows through the county | 342.22 | 172,139 | 503 sq mi(1,303 km2) | |
| Jackson County | 063 | Marianna | 1822 | Escambia | Andrew Jackson (1767–1845), the seventh President of the United States | 54.56 | 49,980 | 916 sq mi(2,372 km2) | |
| Jefferson County | 065 | Monticello | 1827 | Leon | Thomas Jefferson (1743–1826), the third President of the United States and principal author of the Declaration of Independence | 26.62 | 15,921 | 598 sq mi(1,549 km2) | |
| Lafayette County | 067 | Mayo | 1856 | Madison | Gilbert du Motier, marquis de La Fayette (1757–1834), French aristocrat and general in the American Revolutionary War | 15.91 | 8,640 | 543 sq mi(1,406 km2) | |
| Lake County | 069 | Tavares | 1887 | Orange and Sumter | Named for the many lakes in the region | 466.11 | 444,204 | 953 sq mi(2,468 km2) | |
| Lee County | 071 | Fort Myers | 1887 | Monroe | Robert E. Lee (1807–1870), commander of the Confederate Army of Northern Virginia in the American Civil War | 1070.84 | 860,959 | 804 sq mi(2,082 km2) | |
| Leon County | 073 | Tallahassee | 1824 | Gadsden | Juan Ponce de León (1474–1521), Spanish explorer who named Florida | 450.51 | 300,488 | 667 sq mi(1,728 km2) | |
| Levy County | 075 | Bronson | 1845 | Alachua | David Levy Yulee (1810–1886), one of the state's original United States Senators | 42.72 | 47,765 | 1,118 sq mi(2,896 km2) | |
| Liberty County | 077 | Bristol | 1855 | Gadsden | The patriotic ideal of liberty | 9.52 | 7,955 | 836 sq mi(2,165 km2) | |
| Madison County | 079 | Madison | 1827 | Jefferson | James Madison (1751–1836), fourth President of the United States | 26.54 | 18,364 | 692 sq mi(1,792 km2) | |
| Manatee County | 081 | Bradenton | 1855 | Hillsborough | The manatee, or sea cow, is native to Florida waters. | 618.56 | 458,352 | 741 sq mi(1,919 km2) | |
| Marion County | 083 | Ocala | 1844 | Alachua, Hillsborough, and Mosquito | Francis Marion (c. 1732–1795), military officer during the American Revolution | 271.63 | 428,905 | 1,579 sq mi(4,090 km2) | |
| Martin County | 085 | Stuart | 1925 | Palm Beach | John W. Martin (1884–1958), governor of Florida at time of creation of the county | 297.96 | 165,666 | 556 sq mi(1,440 km2) | |
| Miami-Dade County | 086 | Miami | 1836 | Monroenamed Dade until 1997 | City of Miami and Francis L. Dade (c. 1793–1835), Major in the United States Army during the Second Seminole War | 1458.61 | 2,838,461 | 1,946 sq mi(5,040 km2) | |
| Monroe County | 087 | Key West | 1823 | St. Johns | James Monroe (1758–1831), fifth President of the United States | 81.15 | 80,908 | 997 sq mi(2,582 km2) | |
| Nassau County | 089 | Fernandina Beach | 1824 | Duval | Duchy of Nassau in Germany | 160.09 | 104,376 | 652 sq mi(1,689 km2) | |
| Okaloosa County | 091 | Crestview | 1915 | Santa Rosa and Walton | A Choctaw word meaning "a pleasant place", "black water", or "beautiful place" | 235.56 | 220,483 | 936 sq mi(2,424 km2) | |
| Okeechobee County | 093 | Okeechobee | 1917 | Osceola and St. Lucie | Lake Okeechobee, which was in turn is from the Hitchiti words for "big water" | 54.74 | 42,369 | 774 sq mi(2,005 km2) | |
| Orange County | 095 | Orlando | 1824 | St. Johnsnamed Mosquito until 1845 | The fruit that was the county's main product | 1689.04 | 1,533,646 | 908 sq mi(2,352 km2) | |
| Osceola County | 097 | Kissimmee | 1887 | Brevard and Orange | Osceola (1804–1838), a leader of the Seminole during the Second Seminole War | 354.05 | 468,058 | 1,322 sq mi(3,424 km2) | |