Gulf Stream, a warm water current in the North Atlantic Ocean. It begins in the Gulf of Mexico as a continuation of the North Equatorial Current. In the Straits of Florida, between Cuba and Florida, the Gulf Stream is 2,000 feet (610 m) deep and 40 miles (64 km) wide and moves about 5 miles per hour (8 km/h). In the open Atlantic it turns northward, broadens, and flows more slowly. It follows the sunken edge of the continent to Cape Hatteras, North Carolina, where it turns seaward and becomes a wandering, northeasterly current. It comes into contact with the main body of the cold Labrador Current off the Grand Banks, south of Newfoundland. Here, dense fogs often occur.

The Gulf Stream proceeds eastward from the Grand Banks. In the Atlantic it weakens, becomes more a drift than a current, and fans out. The main branch, called the North Atlantic Current, or Drift, moves to northwestern Europe, where it tempers the climate. Another part goes southward to the Sargasso Sea; another, the Irminger Current, goes northward toward Iceland and Greenland; and the rest flows eastward toward Spain and then southward as the Canaries Current.