Willem Janszoon Blaeu (1571 - 21 October 1638), also known as Willem Jansz. Blaeu (;, was a Dutch cartographer, globe maker, and publisher. He was one of the leading figures of the Dutch school of cartography in the seventeenth century.

Trained in astronomy under Tycho Brahe between 1594 and 1596, Blaeu established a workshop in Amsterdam where he produced globes, nautical charts, and maps. These works formed the