Arctic sea passage between Ellesmere Island, Can. (west), and northwestern Greenland (east). The sound, 30–45 miles (48–72 km) wide, extends northward for 55 miles (88 km) from Baffin Bay to the Kane Basin.

The sound was discovered in 1616 by William Baffin and named for Sir Thomas Smythe (Smith), promoter of voyages to find a Northwest Passage. It was not until the mid-19th century that any explorer reached a more northern latitude.