The Alps are the great mountain system of central Europe. The mountains stretch for some 800 km (500 miles) from east to west and 160 km (100 miles) from north to south. They curve in a great arc from the Riviera coast on the Mediterranean Sea, along the borders of northern Italy and adjacent regions of southeastern France, Switzerland, southwestern Germany, Austria and into Slovenia. The Alps form the watershed of many of Europe's rivers, including the Rhine, the Rhône, the Po and the Danube.

Geologically, the Alps were formed during the Oligocene and Miocene epochs as a result of the pressure exerted on the Tethyan geosyncline as its Mesozoic and Cenozoic strata were squeezed against the stable Eurasian landmass by the northward-moving African landmass. The squeezing action formed great recumbent folds (nappes) that rose out of the sea and pushed northward, often breaking and sliding one over the other to form gigantic thrust faults. Crystalline rocks, which are exposed in the higher central regions, are the rocks forming Mont Blanc, the Matterhorn and high peaks in the Pennine Alps and Hohe Tauern; limestone and other sedimentary rocks are predominant (but not continuously present) in the generally lower ranges to the north and south. Mont Blanc (4807 m, 15,771 feet) is the highest peak.

Permanently snowcapped peaks rise above the snowline—located between 8,000 ft and 10,000 ft (2,440-3,050 m)—and glaciers (the longest being Aletsch glacier) form the headwaters of many Alpine rivers. Glaciation was more extensive during the Pleistocene epoch and carved a distinctive mountain landscape—characterized as alpine—of arêtes, cirques, matterhorns, U-shaped and hanging valleys, and long moraine-blocked lakes (such as Garda, Como, and Maggiore in the south and Zürich, Geneva, Thun, and Brienz in the north).

The Alps were the first mountain system to be extensively studied by geologists, and many of the geologic terms associated with mountains and glaciers originated there. The term alps has been applied to mountain systems around the world that exhibit similar traits to the Alps of Europe.

Below the snowline is a treeless zone of alpine pastures that have for generations been used for the summer grazing of goats and cattle. Agriculture is confined to the valleys and foothills, with fruit growing and viticulture on some sunny slopes. Hydroelectric power, used for industries in the mountains and in nearby regions, is generated from the many waterfalls and swift-flowing rivers. Tourism, based on the scenic attractions of the Alps and the mountaineering and winter sports they provide, is a major source of income; among the more famous resorts are Chamonix (France); Zermatt, Interlaken, St. Moritz, Davos, and Arosa (Switzerland); Sankt Anton, Innsbruck, Kitzbühel, Salzburg, and Bad Gastein (Austria); Berchtesgaden (Germany); Cortina d'Ampezzo and Bolzano (Italy); and Bled (Slovenia).

The Alps are divided by rivers and other topographic features into more than 40 subunits for which local names are commonly used. Well-known groups in the W Alps (from the Riviera to the Great St. Bernard Pass) include the Maritime, Ligurian, Cottian, and Graian alps, the Mont Blanc group, and Valle d'Aosta. The highest western peaks are Mont Blanc, Mont Pelvoux, Monte Viso, and the Gran Paradiso; the chief routes across this section are via the Mont Cénis Tunnel and the Great and Little St. Bernard passes. The Central Alps (between the Great St. Bernard and Brenner passes) include, in the south, the Pennine, Lepontine, Phaetian, and Ötztal alps; and, in the north, the Bernina, Glarus, Allgäu, and Bavarian alps. The principal peaks of the Central Alps are Monte Rosa, the Matterhorn, the Finsteraarhorn, the Jungfrau, and the Wildspitze; the chief routes are the Simplon Tunnel and the St. Gotthard, Grimsel, Furka, Splügen, Bernina, and Brenner passes. The E Alps comprise, in the south, the Dolomites, the Carnic Alps, and the Julian Alps; and, in the north, the Hohe Tauern and Niedere Tauern; the principal eastern peak is Grossglockner. Most major routes across the E Alps follow the Brenner and Semmering passes.