Willem Janszoon sometimes abbreviated to Willem Jansz who was a Dutch navigator and colonial governor. Janszoon served in the Netherlands East Indies in the periods 1603–11 and 1612–16 including as governor of Fort Henricus on the island of Solor. He is the first European known to have seen the coast of Australia during his voyage of 1605–06.

In 1600 a small Dutch sailing ship named the Duyfken captained by Willem Janszoon set sail from Banten in Indonesia, in search of new trading opportunities. On 26 February 1606 they anchored off the Pennefather River in the Gulf of Carpentaria and went ashore. They found the land swampy and the people there unfriendly. The ship lost ten of its crew on various expeditions on shore. Janszoon named the place "Nieu Zeland" (New Zeland). Janszoon is credited with being the first European to set foot on Australian soil. Janszoon however didn't realise he have discovered Australia. He thought the land was part of the island of New Guinea which is further to the north.