Ski warfare is the use of ski-equipped troops in war.
 Ski warfare is first recorded by the Danish historian Saxo Grammaticus in the 13th century. During the Battle of Oslo in 1161, Norwegian troops used skis for reconnoitering. They were also used in 1452 in Sweden, and in the 15th to 17th centuries by various other Scandinavian countries. Norwegian Captain Jens Emahusen wrote a military ski manual Skiloperegglement in 1733. In 1767, military ski competitions began. They evolved into the biathlon.
 Denmark–Norway (though only Norwegian) ski troops were used against Sweden during the 1807–1814 Napoleonic Wars.
 Just prior and during World War I many combatants deployed ski troops as part of mountain infantry divisions. France created the Briançon military ski school in 1904. The Italian Army raised 88 Alpini Battalions.  Their purpose was to fight summer and winter in the highest regions of the Alpine Arch.  Most of the battalions were dissolved after World War I. Only nine Alpini regiments remain in service today, and only four still train every soldier in ski warfare: the 4th Alpini Parachutist Regiment, 5th Alpini Regiment, 6th Alpini Regiment and 7th Alpini Regiment. France's Chasseurs Alpins, created in 1888, consisted of 12 battalions.  Currently three remain. Romanian Mountain Corps consisted of three battalions. 
The Austro-Hungarian Army had the Kaiserjäger. German Alpenkorps was founded in 1915 with two brigades.
 Ski troops played a key role in the successes of the Finnish war effort against the Soviet Union during the Winter War in 1939. Forested, rural terrain with no roads was used by Finnish ski troops with great success against the advancing mechanized Soviet troops. In the Battle of Suomussalmi, two Soviet mechanized divisions (45,000 men) were annihilated by three Finnish regiments (11,000 men).
 Italian ski troops included the Arditi Alpieri formation, the Monte Bianco formation, the Monte Cervino battalion, and the Monte Rosa battalion. They were deployed in France, the Balkans, and the Soviet Union.
 The Soviet Union deployed 11 ski battalions, among other troops, in November 1941 to reinforce their defenses in the Battle of Moscow.
 The most common transportation for Norwegian soldiers during the Norwegian Campaign in 1940 was skis and sleds, and in Operation Gunnerside, paradropped Norwegian commandos covered a large distance using skis in order to reach and sabotage the heavy water plant Vemork at Rjukan in Telemark, Norway, which was being used by the Germans as part of their nuclear research programme.
 Ski warfare even extended to the Middle East where the Australian Ski Corps were deployed against Vichy French forces in the mountains of Lebanon.
 The United States Army 10th Mountain Division was established and trained for ski combat. They were deployed in Italy.
 Swedish, Finnish and Norwegian defense forces use skis in cross country skiing but also by pulling squads of soldiers with tracked transport vehicles or snow mobiles. One or two ropes hang from the end of a tracked vehicle such as the famous Swedish Hägglunds Bandvagn 206 or the Finnish Sisu Nasu and troops hang onto the ropes with their hands and ski-poles.
 Many nations train troops in skiing and winter warfare, including:
 The Norwegian military have held skiing competitions since the 1670s.  The sport of biathlon was developed from military skiing competitions.
 The United States ski patrol plays a vital role in the plot to the book A Separate Peace.