Dutch navigator and colonial governor Willem Jansz or Willem Janszoon (c. 1570–1630) was the first European known to have sighted the Australian coast during a voyage in 1605–06.
Nothing is known of his early life, though he may have been a foundling and must have received enough education to read, write and master the basics of navigation.
Jansz joined the Oude Compagnie, a predecessor of the VOC in 1598 and made his first voyage to the Indies as mate aboard the Hollandia in the second Dutch fleet under Jacob Cornelisz van Neck. He returned to Holland on 15 July 1599,
He was master of the Lam, in Joris van Spilbergen's three-ship fleet in 1601. Along the way, During the trip, he transferred to the Ram as steersman and was back in Holland on 18 December 1603
He made his third trip east as captain of the Duyfken ("Little Dove"), one of twelve ships in Steven van der Hagen's fleet.
When majority of the fleet set sail for home, Janszoon remained in the Indies to investigate rumours of trade opportunities and gold in uncharted waters southeast of the Spice Islands’
The Duyfken sailed from Bantam on 18 November 1605, bound for the western coast of New Guinea, crossed the eastern end of the Arafura Sea into the Gulf of Carpentaria, and on 26 February 1606 made landfall at the Pennefather River on western Cape York, near modern-day Weipa. Janszoon charted some 320 km of the coastline, which he thought was a southerly extension of New Guinea.
Instead of the fabled Isla del Oro which allegedly had beaches sprinkled with gold, the Dutchmen found a charmless, barren unappealing wasteland, sparsely wooded with low-lying bushes.
Ten of his men were killed on expeditions ashore, nine of them in an incident before the Duyfken crossed Torres Strait, unaware that the waterway was there. After a boat sent to explore an unnamed waterway (possibly the Wenlock or Batavia River) was attacked by a party of hostile Aboriginal men, one of the men received a fatal spear wound. Short of food, firewood and water, with his tiny crew reduced by almost half, Janszoon decided to turn back at Cape Keerweer (Turnagain), south of Albatross Bay.
He arrived back at Bantam in June 1606, having named the land he had discovered "Nieu Zeland", after the Dutch province, but the name was not adopted.
Janszoon’s original journal and log made during the voyage have been lost but his chart, which shows the location of his landfall was still in existence when Hessel Gerritszoon made his Map of the Pacific in 1622. A copy made around 1670 found its way into the Atlas Blaeu Van der Hem, which Prince Eugene of Savoy brought to Vienna in 1730.
Detail from his chart can also be seen in maps of the hemispheres on the floor of The Citizens’ Hall of Amsterdam's Royal Palace.
Written details of the voyage are few, but there is a passage from the journal of Captain John Saris, an Englishman who lived in Bantam from 1605 to 1609 in the 17th Century Purchas his Pilgrimmes, Containing a History of the World in Sea Voyages and Land Travells, by Englishmen and others by Samuel Purchas. Documents from 1618, 1623, and 1644 refer to the expedition and the journal the Carstensz expedition in 1623, contains details of the voyage.
Although Jansz may not have noticed Torres Strait, it appears from instructions to later Dutch expeditions that he may have seen an opening. Those who came after him were told to find out if New Guinea and the land he discovered were a continuous mass or separated by a strait.
After Duyfken returned to Banda, Jansz was given command of a much larger ship, West Friesland as a reward for his competent service. Duyfken joined a fleet of five ships under Cornelis Matelieff at Amboyna that was about to resume the offensive against Portuguese and Spanish interests in the Moluccas.
Jansz and the West Friesland were bound for home, but the disabled vessel was abandoned near Mauritius. While the crew was saved, the cargo was lost. Jansz and the supercargo found their way back to Bantam on the yacht Madagascar.
On his return, Jansz found desultorily employment before an appointment as an upper-merchant on a homebound vessel in January 1611.
He was back in the East in November 1612, served as an upper-merchant and governor of Fort Henricus on Solor and sailed for home at the end of 1616.
Back home in July 1617, he signed up for another stint in the Orient in August. He set out for Java aboard the Mauritius in January 1618, and on 31 July sighted the Australian coastline again near North-West Cape. In Java, he appointed to the Council of the Indies in March 1619 and took part in operations to relieve the fort and destroy the town of Jacatra, then sailed to Tiku on West Sumatra where he captured four English ships. For his part in the campaign, he was awarded a gold chain of honour worth 1,000 guilders.
In 1620, negotiations with the English resulted in an Anglo-Dutch 'Fleet of Defence' which sailed to Manila under Robert Adams to prevent Chinese merchants dealing with the Spanish there. Jansz served as vice-admiral, on an unprofitable cruise, but there were better results when the leadership positions were reversed, the following year.
He was governor of Banda from 1623 to 1627, returned to Batavia in June 1627 and took a fleet of eight vessels on a diplomatic mission to India and Persia. Back in Java in June 1628, he gave Governor-General Coen valuable support when forces from Mataram laid siege to Batavia.
He was one of the three joint-commanders of a fleet which sailed for Holland on 4 December 1628 and reported to the Stadtholder and the States-General on the state of the Indies on 16 July 1629. He is believed to have died in 1630.