Nausiphanes of Teos was a Greek philosopher active in the 4th century BCE. He was a follower of the atomist tradition founded by Democritus, which taught that the physical world is composed of indivisible particles called atoms. He is historically significant primarily as a teacher of the younger philosopher Epicurus, who would go on to found the influential Epicurean school.

Few concrete details of his life are known. He taught in his hometown of Teos. Some ancient sources claim he also studied under the skeptical philosopher Pyrrho, but modern scholars note this association is chronologically difficult and may not be accurate. His relationship with his famous pupil was hostile; Epicurus later publicly rejected Nausiphanes and denied learning from him, despite clear similarities in their thought.

None of Nausiphanes' own writings survive intact. They are known only through fragments and references by later authors. Titles of his works include The Tripod, a textbook on rhetoric and knowledge, and a lost work On Rhetoric. According to ancient accounts, he wrote many texts, though Epicurus accused him of plagiarism.

His importance lies in being a bridge between earlier atomism and Epicureanism. According to modern scholars, he transmitted key Democritean ideas about physics and knowledge to Epicurus. His philosophy combined atomist theory with a focus on rhetoric and practical ethics, aiming at a state of mental calmness or "undisturbedness" (ataraxia), a concept Epicurus later made central to his own system. Despite his pupil's disavowal, Nausiphanes is widely interpreted by academics as a direct and significant influence on the foundations of Epicurean philosophy.