Davis was born at Sandridge near Dartmouth about 1550. From a boy he was a sailor, and early made several voyages with Adrian Gilbert; both the Gilbert and Raleigh families were Devonians of his own neighbourhood, and through life he seems to have profited by their friendship.
In January 1583 he appears to have broached his design of a north-west passage to Walsingham and John Dee; various consultations followed; and in 1585 he started on his first north-western expedition. On this he began by striking the ice-bound east shore of Greenland, which he followed south to Cape Farewell; thence he turned north once more and coasted the west Greenland littoral some way, until, finding the sea free from ice, he shaped a course for China by the north-west. In 66 N., however, he fell in with Baffin Land, and though he pushed some way up Cumberland Sound, and professed to recognize in this the hoped strait, he now turned back (end of August).
He tried again in 1586 and 1587; in the last voyage he pushed through the straits still named after him into Baffins Bay, coasting west Greenland to 73 N., almost to Upernavik, and thence making a last effort to find a passage westward along the north of America. Many points in Arctic latitudes (Cumberland Sound, Cape Walsingham, Exeter Sound, etc) retain names given them by Davis, who ranks with Baffin and Hudson as the greatest of early Arctic explorers and, like Frobisher, narrowly missed the discovery of Hudsons Bay via Hudsons Straits (the Furious Overfall of Davis).
In 1588 he seems to have commanded the Black Dog against the Spanish Armada; in 1589 he joined the earl of Cumberland off the Azores; and in 1591 he accompanied Thomas Cavendish on his last voyage, with the special purpose, as he tells us, of searching that north-west discovery upon the back parts of America. After the rest of Cavendish's expedition returned unsuccessful, he continued to attempt on his own account the passage of the Strait of Magellan; though defeated here by foul weather, he discovered the Falkland Islands. The passage home was extremely disastrous, and he brought back only fourteen of his seventy-six men.
After his return in 1593 he published a valuable treatise on practical navigation in The Seaman's Secrets (1594), and a more theoretical work in The Worlds Hydrographical Description (1595). His invention of backstaff and double quadrant (called a Davis Quadrant after him) held the field among English seamen till long after Hadley's reflecting quadrant had been introduced. In 1596-1597 Davis seems to have sailed with Raleigh (as master of Sir Walter's own ship) to Cadiz and the Azores; and in 1598-1600 he accompanied a Dutch expedition to the East Indies as pilot, sailing from Flushing, returning to Middleburg, and narrowly escaping destruction from treachery at Achin in Sumatra.
In 1601-1603 he accompanied Sir James Lancaster as first pilot on his voyage in the service of the East India Company; and in December 1604 he sailed again for the same destination as pilot to Sir Edward Michelborne (or Michelbourn). On this journey he was killed by Japanese pirates off Bintang near Sumatra.
A Traverse Book made by John Davis in 1587, an Account of his Second Voyage in 1586, and a Report of Master John Davis of his three voyages made for the Discovery of the North West Passage were printed in Hakluyt's collection. Davis himself published The Seaman's Secrets, divided into two Parts (London, 1594), The Worlds Hydrographical Description . - whereby appears that there is a short and speedy Passage into the South Seas, to China, Molucca, Philippina, and India, by Northerly Navigation (London, 1595). Various references to Davis are in the Calendars of State Papers, Domestic (1591-1594), and East Indies (1513-1616). See also Voyages and Works of John Davis, edited by A. H. Markham (London, Hakluyt Society, 1880), and the article John Davys by Sir J. K. Laughton in the Dictionary of National Biography.