Aristippus of Cyrene was a Greek philosopher active in the late 5th and early 4th centuries BCE. Originally from the North African city of Cyrene, he traveled to Athens and became a follower of Socrates. He is recognized as the founder of the Cyrenaic school of philosophy. Ancient accounts describe him as cosmopolitan and adaptable, willing to associate with powerful rulers and known for teaching for a fee, which was unusual among Socrates' immediate circle. The details of his life are largely based on anecdotes recorded by much later historians, so the precise chronology is uncertain.

No writings by Aristippus himself survive, though later sources attribute lost dialogues to him. His philosophical importance comes from establishing the core principles of Cyrenaic thought. According to modern scholars, the Cyrenaics argued that the highest goal in life is the pursuit of pleasure, particularly immediate bodily pleasures. This early form of hedonism was paired with a subjectivist view that we can only truly know our own immediate feelings. His school was later led by his daughter, Arete, and his grandson, who is often credited with systematizing its doctrines. The Cyrenaics are historically significant as a major Socratic tradition and as a direct precursor and contrast to the later, more tranquil hedonism of Epicureanism.