Masuria is located in the southeast of East Prussia and is part of the Prussian mountain ridge, which consists of a terminal moraine belt from the glacial epoch. Its highest hills in Masuria are: Seesker Berg (in Polish: Gora Szeska) 309 m, Tannenkopf (Gora Tatarska) 308 m, Goldaper Berg (Gora Goldapska) 272 m, Wispebberg (Zameczna Gora) 268 m, Fanalberg (Slupowa Gora) 248 m, Pfarrberg (Popowa Gora) 247 m, Brandberg (Jastrzebia Gora) 230 m, Lindenberg (Lipowa Gora) 223 m, Pillacker Berge (Gory Pilaki) 219 m, Jablonker Berge (Jablonskie Gory) 207 m, Räuberberg (Gesia Gora) 206 m, Plowczer Berg (Plowiecka Gora) 205 m, Spitzberg (Ostra Gora) 203 m, Teufelsberg (Diablo Gora) 200 m, Anhaltsberg (Lysa Gora) and Monker Berge 191 m, Fichtenberg (Gora Chojniczka) 190 m, Schedlisker Berge 188 m, Stradauner Berge 187 m, Schafsberg (Owcza Gora) 181 m, Hühnerberg (Gora Kokoszka) 180 m, Soldatenberg and Fuchsberg (Gora Lisa) 177 m, Rabenberg (Krucza Gora) 175 m, Ziegeleienhöhe (Cegielnia Gora) 174 m, Saalberg (Pawlocinska Gora) 168 m, Dragonerberg (Gora Dragonier) 164 m, Skomaniberg (Skomeck Gora) 156 m, Schlossberg (Gora Zamkowa) 147 m, Bürknerhöhe (Wzgorza Mazurskie) 145 m, Tatarenberge (Tatary Gory) 144 m, Töpferberg (Zdunowa Gora) 136 m and Weisser Berg (Biala Gora) 132 m.

To the south there are extensive sandy areas formed by depositings of glacial meltwater streams. Areas of sandy heathland covered with pine trees, such as the woodlands "Johannisburg Heath" (Puszcza Piska) (1,004.7 km²) and "Ortelsburg Heath", belong to them.

Masuria can be divided into two parts: the hilly-country Masuria north of the line Jedwabno - Ortelsburg - Nikolaiken - Lyck and the heathland Masuria south of this line.

Warmia is situated in the west and northwest of Masuria, and Mazovia and Podlasia are located in the south and southeast of Masuria. Today Masuria belongs to the Polish administrative district of "Warmia i Mazury".

Masuria is rich in woods and numerous lakes form the Masurian Lake District (Kraina Wielkich Jezior) as well as the Lyck Lake District (Pojezierze Elckie).

Marshes and moors can be found in the districts of Neidenburg, Ortelsburg, Johannisburg and Lyck.

The Masurian borders are not defined by topographical elements, such as mountains or rivers. The geographical name "Masuria" didn't develop until the beginning of the 19th century. Masuria is located in the area of the Old Prussian districts of Sassia, Galindia and Sudovia. During the time of the German Order, Masuria consisted of several commanderies, which were established in areas of the Order colonized before. Masurian areas were added to those commanderies in order to speed up the colonization of Masuria. Even at the end of the 19th century Masuria didn't form an administrative entity. The districts of Neidenburg and Ortelsburg belonged to the administrative district of Königsberg (in Russian: Kaliningrad), and from 1905 onwards to the newly formed administrative district of Allenstein (in Polish: Olsztyn). The districts of Angerburg, Goldap, Johannisburg, Lötzen, Lyck, Oletzko and Sensburg, however, belonged to the administrative district of Gumbinnen (in Russian: Gusev). The southern and eastern borders towards Mazovia and Lithuania haven't changed since the 14th century, although these areas formed either the independent Duchy of Mazovia and the Grand Duchy of Lithuania, the Polish-Lithuanian Union or parts of tsaristic Russia. The border to Warmia was based upon a denominational partition between Protestant Masurians and the Catholic inhabitants of Warmia. Today one won't recognize this partition in the common Catholic county.

Often places outside Masuria claim to belong to Masuria in order to attract tourists, particularly if they can boast of lakes, woods and a largely sound environment. Today the Polish define Masuria, regardless of the historic borders, as countryside in the northeast of Poland which is rich in woods and lakes and where people can go sailing and cycling or ride on horseback in their holidays.