The Usipi were a Germanic tribe whose territory lay on the right bank of the Rhine (and thus outside the Roman Empire, in Germania), probably between the valleys of the Lahn and Sieg. They are mentioned in Ptolemy's Geography and in Tacitus' Germania (chapter 32), where they are described as one of the neighbouring tribes to the Chatti and the Tencteri during the 1st century AD.
They are most notoriously recorded in Tacitus' Agricola (chapter 28), where he recounts how a cohort drafted into the Roman army mutinied whilst on campaign in northern Britain (presumably on the west coast) with his father-in-law, the general Gn. Iulius Agricola (probably in AD 82, although the chronology is disputed). They killed the centurion and regular Roman soldiers based with them for training purposes, then stole three ships and sailed round the northern end of Britain, their hardships including being driven to cannibalism by shortage of food. They finally made landfall in the territory of the Suebi, where some were captured by that tribe. Others were caught by the Frisii and a few survivors were sold into slavery to tell their tale.
Dio Cassius tells a similar (if rather simplified) story but places the events a few years earlier.
See also 
- Tacitus, Germania.XXXII