Chrysippus of Soli was a Greek philosopher of the 3rd century BCE. He is best known as the third head of the Stoic school in Athens, a role he assumed around 230 BCE. Originally from Soli in Cilicia (modern Turkey), he moved to Athens to study philosophy. He first studied under the skeptical philosopher Arcesilaus before becoming a disciple of Cleanthes, the second Stoic leader. Ancient sources describe him as an exceptionally prolific writer and a master of logical argument.

According to later historians, Chrysippus wrote over 700 works covering the full range of Stoic thought: logic, physics, and ethics. None of these writings survive in complete form. They are known only through fragments and summaries quoted by later authors like Plutarch, Cicero, and Diogenes Laertius. Some of his notable lost works included treatises On the Soul, On Providence, and On Ends.

Modern scholars regard Chrysippus as the second founder of Stoicism, after its originator Zeno of Citium. He is credited with rigorously systematizing Stoic doctrine, defending it against critics, and expanding its theories. A key contribution was his development of compatibilism, the argument that fate and human free will are compatible. His writings became the standard reference for Stoic philosophy, shaping the school for centuries and making him a central figure in Hellenistic debates. His death around 205 BCE is humorously reported in some ancient anecdotes, but the exact circumstances are uncertain.