Olsztyn is the capital of the Warmia and Mazury region, located at its very heart in the middle. It is situated in the southern part of Warmia, a historical land, which in the years 1466-1772 belonged to the Republic of Poland.
The city is adjacent to six municipalities: Dywity, Barczewo, Purda, Stawiguda, Gietrzwałd and Jonkowo. They all belong to the County of Olsztyn, whose office is located in Olsztyn itself.

From the south, the city is bordered by a forest complex (Puszcza Napiwodzko-Ramucka).

21% of Olsztyn is occupied by woods whose main component is the extensive Town Forest. The main river flowing through Olsztyn - from south to north - is the Łyna. It originates from abundant springs at 153m above sea level, and in Olsztyn it flows at the level of 98m.Within the city borders there are also the Wadąg and Kortówka rivers.

In the area of Olsztyn there are 15 lakes (including 13 with more than 1ha). They occupy a total of approximately 725ha (more than 8% of the city’s whole area). Residents also enjoy the recreational value of reservoirs located close to the city borders, such as the Wadąg, Bartążek or Kielarskie lakes.
The highest point of Olsztyn lies at an altitude of 155m above sea level, and the lowest at 88m. The climate of the city is described as moderately warm. It has the features of a lake district climate with low temperatures, frequent early and late frosts and strong winds. Precipitation in the year reaches 600mm. The average July temperature is around 18°C, and in January around -4°C.

This largest city of Warmia and Mazury lies in a physiographic mesoregion, which is a part of the macro-region of the Mazurian Lake District. This in turn forms part of the lake districts of the eastern subprovince, belonging to the province of the East Baltic-Belarusian Lowland. Olsztyn Lake District covers an area of approximately 3820km2. From the north - adjacent to the Ornecka Plain, Górowskie Hills and Sępopolska Plain, from the east – the Mrągowo Lake District, from the south – Mazurska Plain and Lubawski Hump and from the west – the Iława Lake District.