Internationally, Montenegro borders Croatia, Bosnia and Herzegovina, Serbia, Kosovo, and Albania. It lies between latitudes 41° and 44° N, and longitudes 18° and 21° E.

Montenegro ranges from high peaks along its borders with Serbia and Albania, a segment of the Karst of the western Balkan Peninsula, to a narrow coastal plain that is only one to four miles (6.4 km) wide. The plain stops abruptly in the north, where Mount Lovcen and Mount Orjen plunge into the inlet of the Bay of Kotor.

Montenegro's large Karst region lies generally at elevations of 1,000 metres (3,280 ft) above sea level; some parts, however, rise to 2,000 m (6,560 ft), such as Mount Orjen (1,894 m or 6,214 ft), the highest massif among the coastal limestone ranges. The Zeta River valley, at an elevation of 500 m (1,600 ft), is the lowest segment.

The mountains of Montenegro include some of the most rugged terrain in Europe, averaging more than 2,000 metres in elevation. One of the country's notable peaks is Bobotov Kuk in the Durmitor mountains, which reaches a height of 2,522 metres (8,274 ft). Owing to the hyperhumid climate on their western sides, the Montenegrin mountain ranges were among the most ice-eroded parts of the Balkan Peninsula during the last glacial period.

• Longest beach: Velika Plaza, Ulcinj - 13,000 m (8.1 mi)
• Highest peak: Zla Kolata, Prokletije at 2,534 m
• Largest lake: Skadar Lake - 391 km² (151 sq mi) of surface area
• Deepest canyon: Tara River Canyon - 1,300 m (4,300 ft)
• Biggest bay: Bay of Kotor
• National parks: Durmitor - 390 km² (150 sq mi), Lovcen - 64 km² (25 sq mi), Biogradska Gora - 54 km² (21 sq mi), Skadar Lake - 400 km² (154 sq mi) and Prokletije.
• UNESCO World Heritage sites: Durmitor and Tara River Canyon, old city of Kotor.

Montenegro is a member of the International Commission for the Protection of the Danube River (ICPDR), as more than 2,000 square kilometres (772 sq mi) of the country's territory lie within the Danube catchment area.

Crna Gora, sometimes transliterated as Tsrna Gora ("Black Mountain"), is used to denote a larger part of Montenegro in the 15th century. It had in the late 14th century only referred to a small strip of land of the Pastrovici, but eventually came to be used for a wider mountainous region after the Crnojevic family in Upper Zeta.

The aforementioned region became known as Old Montenegro by the 19th century to distinguish it from the newly acquired territory of Brda (The Highlands). Montenegro further increased its size several times by the 20th century as the result of wars against the Ottomans, which saw the annexation of Old Herzegovina and parts of Metohija and southern Rashka. The nation has changed little since that time, though it lost Metohija and gained the Bay of Kotor.

The country's name in most Western European languages reflects an adaptation of the Italian-Venetian calque monte negro (modern Italian would be monte nero), meaning "black mountain", which probably dates back to the era of Venetian hegemony over the area in the Middle Ages. Other languages, particularly nearby ones, use their own direct translation of the term "black mountain".