Julia Drusilla (39 AD-41 AD) was the only child and daughter of Roman Emperor Gaius (Caligula) and his fourth and last wife Caesonia.

Named after her late aunt and her father's favorite sister, Drusilla, Julia was born not long after Caligula married Caesonia (some sources have her being born on the same day as the marriage). Caesonia already had a few children from previous marriages. When Drusilla was born, Caligula took her to a temple that housed statues of goddesses and placed her on the lap of Minerva, instructing the goddess to nurse and train his new daughter. Soon after her birth, Caligula set up donation boxes around Rome marked "Julia's Drink" or "Julia's Food".

The limited available knowledge of Drusilla is not flattering. It is doubtful whether Caligula instilled any discipline in his daughter, amused by the savage nature that has been attributed to her by ancient sources like Suetonius. It is said that when she was old enough to start playing with other children, she would attack them and try to claw out their eyes. Caligula is reported to have said that this was proof that she was his daughter.

On January 24, 41 AD Caligula was assassinated by his guards. Caesonia and Drusilla survived him by only a few minutes. They were killed by his Praetorian Guard under Cassius Chaerea and Drusilla's head was smashed against a wall.