Irregular military
Camisards – Huguenot insurgency in the beginning of the 18th century in the Cévennes
Cateran - Scottish clan warriors and marauders pre-18th century.
Çetes - Muslim irregulars Asia Minor 1910s-1920s
Cheta - armed bands resisting Ottoman rule in Macedonia, early 20th century.
Chetniks - nationalist movement and guerrilla force in occupied Yugoslavia 1941-44.
Croats (military unit) - 17th century frontier light cavalry in Habsburgh service.
Dubat - indigenous auxiliaries in Italian Somaliand.
Fano - Ethiopian guerrilla force
Fedayeen - Arabic term for fighters willing to sacrifice themselves
Fellagha - nationalist militants in Algeria and Tunisia opposing French colonial rule 1950s.
Filibuster (military) - participants in foreign military interventions without official backing.
Free Corps (Freikorps) – volunteer units in German-speaking countries, that existed from the 18th to the early 20th centuries as private armies
Free Swarm (Freischar) – volunteers, that participated in a conflict without the formal authorisation of one of the belligerents, but on the instigation of a political party or an individual
Goumiers – originally tribal allies supporting France in Algeria during the 19th century. From 1912 to 1956 Moroccan auxiliaries serving with the French Army.
Hajduks— bandits and irregulars in and against the Ottoman Empire, but found amongst military ranks in Hungary and the Polish–Lithuanian Commonwealth
Harkis – Algerian Muslim irregulars who served with the French Army during the Algerian War of 1954–62.
Haydamak - pro-Cossack paramilitary (18th century)
Honghuzi – Manchurian bandits who served as irregulars during the Russo-Japanese War of 1904–1905.
Jagunço – armed hand in Northern Brazil.
Kachaks - Albanian bandits and rebels (1880s–1930)
Klephts – Greek guerrilla fighters in Ottoman Greece
Komitadji – rebel bands operating in the Balkans during the final period of the Ottoman Empire.
Kuruc - Hungarian insurgent groups 17th-18th centuries.
Kuva-yi Milliye - Ottoman/Turkish militia 1918-1921
Land Storm (troops) (Landsturm) – created by a 21 April 1813 edict of Frederick William III of Prussia, lowest level of reserve troops in Prussia, Germany, Austria-Hungary, Sweden, Switzerland and the Netherlands
Legion of Frontiersmen – An irregular quasi-military organization that proliferated throughout the British Empire prior to World War I
Macheteros de Jara - Paraguayan cavalry regiment of the Chaco War
Republiquetas
Requeté
Makhnovshchina – Ukrainian anarchist army that fought both the White Armies and the Bolsheviks during the Russian Civil War.
Minutemen – American irregular troops during the American Revolution
Morlachs - Dalmatian auxiliaries in Venetian service during the 17th century.
People's Liberation Armed Forces of South Vietnam- Viet Cong's army
Pindari – 18th century irregular horsemen in India
Rapparee - Irish guerillas (1690s)
Righteous Army— militias organised at several dates in Korean history
Rough Riders – in the Spanish–American War
Ruga-Ruga - East African auxiliaries to German and British colonial armies.
Selbstschutz
Shifta – local militia in the Horn of Africa,
Trenck's Pandurs – Habsburg monarchy 17th and 18th century skirmisher, later evolving in the regular Grenz infantry.
Zapatistas - militant political movement active in southern Mexico from 1994.
Zeybeks - Ottoman irregulars (17th to 20th centuries)

Irregulars in today's warfare: Modern conflicts in post-invasion Iraq, the renewed Taliban insurgency in the 2001 war in Afghanistan, the Darfur conflict, the rebellion in the North of Uganda by the Lord's Resistance Army, and the Second Chechen War are fought almost entirely by irregular forces on one or both sides.
The CIA's Special Activities Center (SAC) is the premiere American paramilitary clandestine unit for creating or combating irregular military forces. SAD paramilitary officers created and led successful units from the Hmong tribe during the Laotian Civil War in the 1960s and 1970s. They also organized and led the Mujaheddin as an irregular force against the Soviet Union in Afghanistan in the 1980s, as well as the Northern Alliance as an irregular insurgency force against the Taliban with US Army Special Forces during the war in Afghanistan in 2001 and organized and led the Kurdish Peshmerga with US Army Special Forces as an irregular counter-insurgency force against the Kurdish Sunni Islamist group Ansar al-Islam at the Iraq-Iran border and as an irregular force against Saddam Hussein during the war in Iraq in 2003.
Irregular civilian volunteers also played a large role in the Battle of Kyiv during the 2022 Russian Invasion of Ukraine.

See also: Asymmetric warfare – Military theory that also includes regulars vs. irregulars
Fourth generation warfare
"Yank" Levy, teacher of the Home Guard and coauthor of the first practical book on Guerrilla Warfare
Low intensity conflict
Military volunteer
Unconventional warfare
Violent non-state actors
Sissi (Finnish light infantry)

Legal aspects, categories: Definition of terrorism
Enemy combatant, US term used during the "War on Terror"
Law of war
Martens Clause, stating that customary law applies where specific law is lacking in detail
Unlawful combatant

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Further reading: Beckett, I. F. W. (15 September 2009). Encyclopedia of Guerrilla Warfare (Hardcover). Santa Barbara, California: Abc-Clio Inc. ISBN 978-0874369298.