Situated in southern Europe, the Italian Republic, including the major islands of Sicily (Sicilia) and Sardinia (Sardegna), covers a land area of 301,230 sq km (116,306 sq mi). Comparatively, the area occupied by Italy is slightly larger than the state of Arizona. The boot-shaped Italian mainland extends into the Mediterranean Sea with a length of 1,185 km (736 mi), southeast to northwest, and a width of 381 km (237 mi), northeast to southwest.

It is bordered on the north by Switzerland and Austria, on the northeast by Slovenia, on the east by the Adriatic and Ionian seas, on the west by the Tyrrhenian and Ligurian seas, and on the northwest by France, with a total land boundary length of 1,932 km (1,200 mi) and a coastline of 7,600 km (4,712 mi). Situated off the toe of the Italian boot, Sicily has a surface area of 25,708 sq km (9,926 sq mi). Sardinia, which is about 320 km (200 mi) northwest of Sicily, covers an area of some 24,090 sq km (9,300 sq mi).

Within the frontiers of Italy are the sovereign Republic of San Marino, with an area of 61.2 sq km(23.6 sq mi), and the sovereign state of Vatican City, which covers 44 hectares (108.7 acres).

The long-disputed problem of Trieste, a 518 sq km (200 sq mi) area situated at the head of the Adriatic Sea, between Italy and Yugoslavia, was resolved in 1954, when Italy assumed the administration of Zone A, the city and harbour of Trieste, and Yugoslavia of Zone B, the rural hinterlands of the Istrian Peninsula. A treaty of October 1975 made the partition permanent. Italy's capital city, Rome, is located in the west-central part of the country.

Except for the fertile Po River Valley in the north and the narrow coastal belts farther south, Italy's mainland is generally mountainous, with considerable seismic activity. During Roman times, the city of Pompeii, near present-day Naples (Napoli), was devastated first by an earthquake in AD 63 and then by the famed eruption of Mt. Vesuvius (1,277 m/4,190 ft) in AD 79. In the last century, an earthquake in northeastern Italy on 6 May 1976 left more than 900 people dead, and a quake in the south on 23 November 1980 (and subsequent aftershocks) claimed at least 4,500 lives.

The Alpine mountain area in the north along the French and Swiss borders includes three famous lakes – Como, Maggiore and Garda – and gives rise to six small rivers that flow southward into the Po. Italy's highest peaks are found in the northwest in the Savoy Alps, the Pennines and the Graian chain. They include Mont Blanc (4,807 m/15,771 ft), on the French border; Monte Rosa (Dufourspitze, 4,634 m/15,203 ft) and the Matterhorn (Monte Cervino, 4,478 m/14,692 ft), on the Swiss border; and Gran Paradiso (4,061 m/13,323 ft). Marmolada (3,342 m/10,965 ft), in northeast Italy, is the highest peak in the Dolomites.