Sostratus of Nyssa was a Hellenistic grammarian active in the 1st century BCE. His birthplace, Nyssa, could refer to cities in Caria or Cappadocia. No specific biographical details about his life or education survive.

He is known for a single, now-lost work: a collection of mythological and historical paradoxa, or marvelous tales. It survives only in fragments, primarily through citations by the later compiler Athenaeus of Naucratis in his Deipnosophistae. Athenaeus quotes Sostratus for anecdotes concerning luxurious foods and dining customs, indicating the collection’s focus on gastronomic and historical curiosities.

As a compiler of paradoxa, Sostratus represents a Hellenistic scholarly tradition dedicated to collecting rare and noteworthy information. His work served as a source for later encyclopedic writers like Athenaeus, thereby helping to preserve fragments of Hellenistic learning. This places him within the broader context of grammarians and antiquarians who systematized cultural knowledge.