The Cherusci were a Germanic tribe that inhabited parts of the plains and forests of northwestern Germania in the area of the Weser River and present-day Hanover during the first centuries BCE and CE. Roman sources reported they considered themselves kin with other Irmino tribes and claimed common descent from an ancestor called Mannus.

During the early Roman Empire under Augustus, the Cherusci first served as allies of Rome and sent sons of their chieftains to receive Roman education and serve in the Roman army as auxiliaries. The Cherusci leader Arminius led a confederation of tribes in the ambush that destroyed three Roman legions in the Teutoburg Forest in CE 9. He was subsequently kept from further damaging Rome by disputes with the Marcomanni and reprisal attacks led by Germanicus.

After rebel Cherusci killed Arminius in CE 21, infighting among the royal family led to the highly Romanized line of his brother Flavus coming to power. Following their defeat by the Chatti around CE 88, the Cherusci do not appear in further accounts of the German tribes, apparently being absorbed into the late classical groups such as the Saxons, Thuringians, Franks, Bavarians, and Allemanni.

Cherusci (Latin: [kʰeːˈrus.kiː]) is the Latin name for the tribe. Both it and the Greek form Khēroûskoi (Χηροῦσκοι) are presumably transcriptions of an otherwise unattested Old Germanic demonym, whose etymology is unclear. The dominant opinion in scholarship is that it may derive from *herut ("hart"), which may have had totemistic significance for the group. Another hypothesis—proposed in the 19th century by Jacob Grimm and others—derives the name from *heru- (Gothic: hairus; heoru, a kind of sword). Hans Kuhn has argued that the derivational suffix -sk- involved in both explanations is uncommon in Germanic. He suggested that the name may therefore be a compound of ultimately non-Germanic origin and connected to the hypothesized Nordwestblock.

The Cherusci were a Germanic tribe living around the central Weser River in the 1st century BCE and 1st century CE. They are first attested in Julius Caesar's Commentaries on the Gallic War. Caesar relates that in the year 53 BCE he crossed the Rhine to punish the Suebi for sending reinforcements to the Treveri. In passing, he mentions that the Suebi were separated from the Cherusci by the "Bacenis Forest", a relatively impenetrable beech forest, possibly the Harz. Pliny grouped them with the nearby Suebi, Chatti, and Hermunduri as Irminones, tribes who claimed descent from an ancestor named Mannus. Tacitus later placed them between the Chatti and the Chauci, generally taken to indicate a territory between the Weser and Elbe.

As part of his German campaigns, Drusus marched an army east into the territory of the Cherusci in 11 BCE and was ambushed as he returned west at a narrow pass called Arbalo, probably near modern Hameln or Hildesheim. The Cherusci were initially victorious but paused their attack, allowing the surviving Romans to break through the encirclement and escape. By that winter, Drusus had recovered enough control that a garrison was stationed somewhere in Cheruscan territory, probably at either Haltern or Bergkamen in North Rhine-Westphalia. The Cherusci continued to resist the campaigns of Tiberius, L. Domitius Ahenobarbus, and M. Vinicius as late as the "vast war" begun around 2 BCE.

Finally, in CE 4, Tiberius overcame the factions of the Cherusci still hostile to Rome and by the next year he considered the tribe a Roman ally, giving it special privileges. The chieftain Segimer sent at least two sons who became Roman citizens and served in the Roman military as cavalry auxiliaries. The elder son Arminius returned as an auxiliary commander under P. Quictilius Varus, who began organizing Germany as the new province of Germania Magna in CE 7. This involved expanded taxation and demands of tribute, and Arminius began organizing a combined attack on Varus's legions. A Cheruscan noble named Segestes attempted to warn the governor repeatedly, but Varus ignored him and followed Arminius into an ambush in the Teutoburg Forest and marshes in CE 9. Working together, the Cherusci, Bructeri, Marsi, Sicambri, Chauci, and Chatti completely destroyed the 17th, 18th, and 19th Legions; Varus and many of the officers fell on their swords during the battle. Cassius Dio reports that Segimer was second in command during the battle but Arminius seems to have acted as chieftain himself soon thereafter. He abducted Segestes's daughter Thusnelda and married her.

The Romans encouraged the Marcomanni to attack the Cherusci and launched punitive raids of their own, eventually recovering some of the lost eagle standards from the defeated legions. In CE 14, Germanicus raided the Chatti and Marsi with 12,000 legionnaires, 26 cohorts of auxiliaries, and eight cavalry squadrons and systematically laid waste to an area 50 miles wide such that "no sex, no age found pity". He then campaigned against the Cherusci, freeing Segestes from captivity and seizing the pregnant Thusnelda. Arminius assembled the Cherusci and surrounding tribes while Germanicus marched some men east from the Rhine and sailed others from the North Sea up the Ems, attacking the Bructeri on their way. These two forces met and then ravaged the land between the Ems and the Lippe. When they reached the Teutoburg Forest, they found the bodies of the slain Romans unburied and in places sacrificed on German altars. The army buried the dead for half a day, after which Germanicus stopped the work to return to war against the Germans. Making his way to the Cherusci heartland, Germanicus was attacked by Arminius's men at Pontes Longi ("the long causeways") in the boggy lowlands near the Ems. The Cherusci trapped and began to kill the Roman cavalry but the Roman infantry was able to check and rout them over the course of a two day battle. Tacitus considered this a victory although historians such as Wells think it was more likely inconclusive.