American Revolutionary War

• Lee's Legion, a military unit of the Continental Army
• Pulaski's Legion, a cavalry regiment of the Continental Army
• Armand's Legion, a dragoon unit of the Continental Army
• British Legion (American Revolutionary War), a military unit of British Provincial Corps
• Lauzun's Legion, a military unit of the French Royal Army

French Revolutionary and Napoleonic Wars

• Légion des Allobroges, an infantry unit of French Revolutionary Army consisting of Swiss and Italian volunteers
• Batavian Legion, an infantry unit of French Revolutionary Army consisting of Dutch volunteers
• Belgian Legion (1792), an infantry unit of French Revolutionary Army consisting of Belgian volunteers
• Legion of Belgians and Liégeois, an infantry unit of French Revolutionary Army consisting of Belgian volunteers
• Irish Legion, an infantry unit of French Army consisting of Irish volunteers
• King's German Legion, a military formation of the British Army consisting of Hanoverian volunteers
• Légion Noire, an infantry unit of the French Revolutionary Army
• Polish Legions (Napoleonic era), units of the French Army consisting of Polish volunteers
• Russian–German Legion, a military formation of the Imperial Russian Army consisting of German, Dutch and Belgian volunteers

Other 18th century legions

• French Revolutionary Legion, an American mercenary force consisting of Anglophone and Francophone volunteers
• Legion of the United States, a temporary reorganization of the United States Army during the Northwest Indian War

World War I

• Czechoslovak Legions, Czech and Slovak volunteer forces fighting on the Allied Powers side
• French Armenian Legion, part of the French Army; also involved in the Franco-Turkish War of 1918–21
• Georgian Legion (1914–1918), a unit of the German Army recruited from Georgians
• Infantry Regiment of the Academic Legion, formed by volunteer Polish students in 1918, later taken into the regular Polish Army
• Italian Legione Redenta, an Italian military formation that participated in the Siberian Intervention during the Russian Civil War
• Jewish Legion, in the British Army at Gallipoli and Palestine
• Polish Legion in Finland, fighting for the Finns against the Russians
• Polish Legions in World War I, part of the Austro-Hungarian Army
• Puławy Legion, a Polish formation that was part of the Imperial Russian Army
• Legion of Ukrainian Sich Riflemen, a corps of the Austro-Hungarian Army

Interwar period

• 2nd Legions Infantry Division (Poland), elite unite of the Polish Army, mostly composed of veterans of the Polish Legions in World War I
• Condor Legion, a unit of "volunteers" from the German Luftwaffe serving with the Nationalists during the Spanish Civil War
• British Legion Volunteer Police Force, a short-lived police force established in response to the outcome of the Munich Agreement in September 1938
• Aviazione Legionaria, Italian air force in the Spanish Civil War

World War II

• Czechoslovak Legion opposing the Germans in Poland, 1939

Note: Except for the above, all World War II legions fought on the German side.

• Free Arabian Legion, Arab volunteers, notably from Iraq, and North Africa fighting on the German side.
• Armenian or Armenische Legion, name given to the 812th Armenian Battalion of the German Army, made up largely of Armenian Red Army prisoners of war
• Azerbaijani Legion (Azerbaijan legion), made up largely of Azerbaijani Red Army prisoners of war
• Blue Legion, Spanish volunteers fighting against the Soviet Union on the Eastern Front
• Crna Legija (Black Legion), the name given to the 1st and 5th Croatian Ustaše Brigades
• Croatian Legion
• Croatian Air Force Legion
• Croatian Anti-Aircraft Legion
• Croatian Naval Legion
• Estonian Legion, a unit in the Waffen SS created in 1942, mainly consisting of Estonian soldiers
• Flemish Legion (Dutch: Vlaams Legioen), recruited among Dutch-speaking volunteers from German-occupied Belgium, notably from Flanders.
• Walloon Legion (French: Légion Wallonie), recruited among French-speaking volunteers from German-occupied Belgium.
• Légion française des combattants (French Legion of Fighters), a pro-Nazi Vichy French unit
• Legion of French Volunteers Against Bolshevism (LVF), pro-Nazi French
• Georgian Legion (1941–1945), a unit of the German army recruited from Georgians
• Indische Legion , also known as the Free India Legion or Tiger Legion, an Indian unit raised in 1941 and attached to the German Army
• Latvian Legion, a formation of the Waffen-SS created in 1943 and consisting primarily of ethnic Latvians
• Legion of St. George, the original name of the British Free Corps
• Ostlegionen (literally "Eastern Legions"), conscripts and volunteers from the occupied eastern territories recruited into the German Army
• La Légion Tricolore , a pro-Nazi French unit which was absorbed into the LVF after six months
• Volga Tatar Legion, one of several units formed by the Wehrmacht out of Soviet prisoners of war according to their ethnicity

Other

• Arab Legion (al-Jaysh al-Arabī) (1920–56), the regular army of Transjordan, predecessor of the present Jordanian Army
• Foreign legion (disambiguation)
  • French Foreign Legion, a unit of the French Army mainly composed of foreigners wishing to fight for France (1831–present)
• Polish Legions (disambiguation), eleven units at different times between the 18th and 20th centuries (some of which are listed separately above)
• Spanish Legion, an elite unit of the Spanish Army (1920–present)