Julia Drusilla (16 September 16 – 10 June 38 AD) was a member of the Roman imperial family, the second daughter and fifth child of Germanicus and Agrippina the Elder to survive infancy.

After the death of her father, Germanicus, she and her siblings were brought back to Rome by their mother and raised with the help of their paternal grandmother, Antonia Minor.

[a] After Caligula became emperor in 37, he ordered their divorce and married his sister to his friend Marcus Aemilius Lepidus.

[1] Rumors reported the brother and sister were lovers from a young age,[9] with their public relationship deemed incestuous by various contemporaries.

[10] Some historians suggest that Caligula was motivated by more than mere lust or love in pursuing intimate relationships with his sisters, instead employing a deliberate pattern for Roman lineage based on the Hellenistic monarchs of the Ptolemaic dynasty, where marriages between jointly ruling brothers and sisters had become tradition rather than sex scandals.

One source of rumors surrounding Caligula and Drusilla may be derived from formal Roman dining habits.

Meanwhile, the widowed husband of Drusilla, Marcus Aemilius Lepidus, reportedly became a lover to her sisters, Julia Livilla and Agrippina the Younger, in an apparent attempt to gain their support so that he could succeed Caligula.