Willem Janszoon (; 1570–1630), sometimes abbreviated to
Willem Jansz., 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.