Gaius Julius Caesar Augustus Germanicus (August 31, 12 – January 24, 41), most commonly known as Caligula, was the third Roman Emperor and a member of the Julio-Claudian dynasty, ruling from 37 to 41. Known for his extreme extravagance, eccentricity, depravity and cruelty, he is remembered as a despot. He was assassinated in 41 by several of his own guards.

The Roman historian Suetonius referred to Caligula as a "monster", and the surviving sources are universal in their condemnation. One popular tale, often cited as an example of his insanity and tyranny, is that Caligula appointed his favourite horse, Incitatus, to a seat on the senate and attempted to appoint it to the position of consul. The story, however, owes its unrelenting currency to its charm: it is based on a single misunderstood near-contemporary reference, in which Suetonius merely repeats an unattributed rumour that Caligula was thinking about doing it (Suet. Cal. 55.3).

Caligula is often alleged to have had incestuous relationships with his sisters, most notably his younger sister Drusilla, but there is no credible evidence to support such claims either.

In short, the surviving sources are filled with anecdotes of Caligula's cruelty and insanity rather than an actual account of his reign, making any reconstruction of his time as Princeps nearly impossible. What does survive is the picture of a depraved, hedonistic ruler, an image that has made Caligula one of the most widely recognizable, if poorly documented, of all the Roman Emperors; the name "Caligula" itself has become synonomous with wanton hedonism, cruelty, tyranny, and insanity. To this day this is reflected in the prices of his coinage on the numismatic market, as it is for his later contemporary, being Nero; for the sole use of vanity jewelry.