Fat Deer Key is an island[1] in the middle Florida Keys.[2]
 Mangrove Beach in Fat Deer Key | |
  Fat Deer Key Fat Deer Key  Fat Deer Key Fat Deer Key (Caribbean) | |
| Geography | |
|---|---|
| Location | Gulf of Mexico |
| Coordinates | 24°44′20″N 81°00′07″W / 24.73889°N 81.00194°W |
| Archipelago | Florida Keys |
| Adjacent to | Florida Straits |
| Administration | |
| State | Florida |
| County | Monroe |
U.S. 1 (or the Overseas Highway) crosses the key near mile markers 53.5-56, between Long Point Key and Key Vaca.
It is entirely within the cities of Marathon, Florida and Key Colony Beach, Florida.
It has the only road leading to the city of Key Colony Beach, known as Sadowski Causeway.