Warlord is a term that refers to a person with power who has de facto military control of a subnational area, due to armed forces loyal to the warlord and not to a central authority. It can also mean one who espouses the ideal that war is necessary, and has the means and authority to engage in war. The word has a strong connotation that the person exercises far more power than his official title or rank (if any) legitimately permits him. Under feudalism, in contrast, the local military leader may enjoy great autonomy and a personal army, but still derives legitimacy from formal fealty to a central authority.

Warlordism was coined to describe chaos at the birth of the Republic of China, especially after the death of Yuan Shikai, as the warlord era. It can however be used to describe similar periods in other countries or epochs such as in Japan during the Sengoku period, or in China during the Three Kingdoms, or in Somalia or other failed states today (2006).

The word "warlord" arose as translation from the German word "Kriegsherr" with the same meaning. Today the Germans often use the English word, which has overtaken "Kriegsherr" in their language. The term "Lord of war" is a misinterpretation of "warlord" used by a character in the 2005 film of the same name (Lord of War), depicting modern warlords and gunrunning.

Warlordism in Europe is usually connected to various mercenary companies and their chieftains, which often were de facto powerholders in the areas in which they resided. Such free companies would arise in a situation when the recognized central power had collapsed, such as in the Great Interregnum in Germany (1254-1278) or in France during the Hundred Years' War after the Battle of Poitiers. Free company mercenary captains, such as Sir John Hawkwood, Roger de Flor of Catalan Company or Hugh Calveley could be considered as warlords. Several condottieri in Italy can also be classified as warlords.

The Imperial commanders-in-chief during the reign of Emperor Maximilian I did hold the title Kriegsherr of which the direct translation was "warlord", but they were not warlords in the definitive sense of the word.

During most of the 16th century, before the Tokugawa era, Japan was tormented by repeated wars among rival warlords (see Sengoku Era). Each warlord had several castles, neighbouring land with peasants and a private army of samurai.

• Oda Nobunaga
• Uesugi Kenshin
• Takeda Shingen
• Hōjō Sōun
• Toyotomi Hideyoshi

Warlords exercised widespread rule in China several times in Chinese history, notably in the period from the Xinhai Revolution when numerous provinces rebelled and declared their independence from the Qing Dynasty in 1911, and especially after Yuan Shikai's death, until the Northern Expedition in 1927 in a period known as the Warlord Era. This is the time when the term "warlord" first appeared. Despite the superficial unification of China in 1927 under the rule of the Kuomintang under Chiang Kai-shek, warlordism remained a problem until the victory of the Communist Party of China in 1949.^{[citation needed]}

The Chinese warlords are depicted in the computer game "Hearts of Iron" and its sequel "Hearts of Iron 2", which are both banned in mainland China. Another popular game with a similar plot is the "Dynasty Warriors" series. These feature many real historic warlords as generals in or leaders of their respective dynasties. Some main characters include prominent Three Kingdoms figures.

• Gongsun Kang
• Gongsun Yuan
• Gongsun Zan
• Dong Zhuo
• Yuan Shao
• Yuan Shu
• Sun Jian
• Sun Ce
• Sun Quan
• Cao Cao
• Cao Pi
• Liu Bei
• Liu Biao
• Lu Bu
• Ma Teng
• Ma Chao

• Puxian Wannu

There were twelve warlords who served as Area Commanders officially:

• Zhang Zuolin (Chang Tso-lin) -- "Old Marshal", "Rain Marshal" or "Mukden Tiger".
• Zhang Xueliang (Chang Hsüeh-liang) -- "Young Marshal".
• Zhang Zongchang (Chang Tsung-ch'ang) -- "The Dogmeat General".
• Feng Yuxiang (Feng Yü-hsiang) -- "The Christian General".
• Bai Chongxi (Pai Ch'ung-hsi) -- "The Muslim General".
• Yan Xishan (Yen Hsi-shan) -- "The Model Governor".
• Wu Peifu -- "The Jade Marshal".

Warlordism appears in so-called failed states - states in which central government and nationwide authorities have collapsed or exist merely formally without actual control over the state territory. They are usually defined by a high level of clientelism, low bureaucratic control and a high motivation in prolonging war for the maintenance of their economic system, mainly based on the extraction of natural resources.

Examples:

• Somalia: With the collapse of the central government, groups of rival warlords constitute the only form of authority in some parts of the country.
• Other regions and countries with warlords include Afghanistan, Chechnya, Burma, Colombia, the Democratic Republic of the Congo, and Pakistan.

• Warlord era
• Warlord (British comics)
• Warlord (comics)
• Warlord (miniature game)
• Warlords
• alt.fan.warlord
• List of warlords