The Eight Banners (in Manchu: ᠵᠠᡴᡡᠨ
ᡤᡡᠰᠠ jakūn gūsa, Chinese: 八旗; pinyin: bāqí; Wade–Giles: pa¹-ch'i², Mongolian: ᠨᠠᠶᠢᠮᠠᠨ
ᠬᠣᠰᠢᠭᠤ) were administrative and military divisions under the Later Jin and Qing dynasties of China into which all Manchu households were placed. In war, the Eight Banners functioned as armies, but the banner system was also the basic organizational framework of all of Manchu society. Created in the early 17th century by Nurhaci, the banner armies played an instrumental role in his unification of the fragmented Jurchen people (who would later be renamed the "Manchu" under Nurhaci's son Hong Taiji) and in the Qing dynasty's conquest of the Ming dynasty.

As Mongol and Han forces were incorporated into the growing Qing military establishment, the Mongol Eight Banners and Han Eight Banners were created alongside the original Manchu banners. The banner armies were considered the elite forces of the Qing military, while the remainder of imperial troops were incorporated into the vast Green Standard Army. Membership in the banners became hereditary, and bannermen were granted land and income. After the defeat of the Ming dynasty, Qing emperors continued to rely on the Eight Banners in their subsequent military campaigns. After the Ten Great Campaigns of the mid-18th century the quality of the banner armies declined. Their failure to suppress the Taiping Rebellion of the mid-19th century ruined their reputation. By the late 19th century the task of defending the empire had largely fallen upon regional armies such as the Xiang Army. Over time, the Eight Banners became synonymous with Manchu identity even as their military strength vanished.

Initially, Nurhaci's forces were organized into small hunting parties of about a dozen men related by blood, marriage, clan, or place of residence, as was the typical Jurchen custom. In 1601, with the number of men under his command growing, Nurhaci reorganized his troops into companies of 300 households. Five companies made up a battalion, and ten battalions a banner. Four banners were originally created: Yellow, White, Red, and Blue, each named after the color of its flag. By 1614, the number of companies had grown to around 400. In 1615, the number of banners was doubled through the creation of "bordered" banners. The troops of each of the original four banners would be split between a plain and a bordered banner. The bordered variant of each flag was to have a red border, except for the Bordered Red Banner, which had a white border instead.

The banner armies expanded rapidly after a string of military victories under Nurhaci and his successors. Beginning in the late 1620s, the Jurchens incorporated allied and conquered Mongol tribes into the Eight Banner system. In 1635, Hong Taiji, son of Nurhaci, renamed his people from Jurchen to Manchu. That same year the Mongols were separated into the Mongol Eight Banners (Manchu: ᠮᠣᠩᡤᠣ
ᡤᡡᠰᠠ, monggo gūsa; Chinese: 八旗蒙古; pinyin: bāqí ménggǔ; Mongolian: Монгол найман хошуу).

Under Hong Taiji, the banner armies participated in two invasions of Joseon in the Korean Peninsula first in 1627 and again in 1636. As a consequence, Joseon was forced to end its relationship with the Ming and become a Qing tributary instead.

Initially, Han troops were incorporated into the existing Manchu Banners. When Hong Taiji captured Yongping in 1629, a contingent of artillerymen surrendered to him. In 1631, these troops were organized into the so-called Old Han Army under the Han commander Tong Yangxing. These artillery units were used decisively to defeat Ming general Zu Dashou's forces at the siege of Dalinghe that same year. In 1636, Hong Taiji proclaimed the creation of the Qing dynasty.

Between 1637 and 1642, the Old Han Army, mostly made up of Liaodong natives who had surrendered at Yongping, Fushun, Dalinghe, etc., were organized into the Han Eight Banners (Manchu: ᠨᡳᡴᠠᠨ
ᠴᠣᠣᡥᠠ nikan cooha or ᡠᠵᡝᠨ
ᠴᠣᠣᡥᠠ ujen cooha; Chinese: 八旗漢軍; pinyin: bāqí hànjūn; Mongolian: Хятад найман хошуу). The original Eight Banners were thereafter referred to as the Manchu Eight Banners (Manchu: ᠮᠠᠨᠵᡠ
ᡤᡡᠰᠠ, manju gūsa; Chinese: 八旗滿洲; pinyin: bāqí mǎnzhōu; Mongolian: Манжийн Найман хошуу). Although still called the "Eight Banners" in name, there were now effectively twenty-four banner armies, eight for each of the three main ethnic groups (Manchu, Mongol, and Han).

Among the Banners gunpowder weapons, such as muskets and artillery, were specifically wielded by the Han Banners.