It was created on 1 January 1999 out of the former Olsztyn and parts of Suwalki and Elblag voivodships as a result of Local Government Reogranization Act of 1998. The voivodship's name recalls the region's two historical lands of Warmia (German: Ermland) and Masuria (Mazury).

The territory is just south of Russia's Kaliningrad Oblast. It was once the southern part of East Prussia.

Major cities and towns

• Olsztyn (177.200)
• Elblag (130.800)
• Elk (57.200)
• Ostroda (35.400)
• Ilawa (34.000)
• Gizycko (31.500)
• Ketrzyn (30.100)
• Szczytno (27.000)
• Bartoszyce (26.400)
• Mragowo (23.400)
• Dzialdowo (21.100)