The Letters of Anaximenes of Miletus are a work from the 4th century BCE, but they were not written by the famous early philosopher Anaximenes. The historical Anaximenes lived in the 6th century BCE in Miletus and was known for his philosophical theory that air was the fundamental substance of the universe. The letters are a later pseudepigraphic creation, meaning they were forged in his name by an unknown author.

This collection is a rhetorical exercise, part of a common Classical practice of inventing correspondence for famous historical figures. The letters survive only in fragments, preserved through quotations by later ancient writers. According to modern scholars, their primary significance lies in illustrating the ancient educational and literary technique of rhetorical impersonation. They show how later generations used the names of early thinkers to create ethical or biographical scenarios, reflecting Anaximenes' lasting reputation rather than providing any factual information about him. The work is therefore studied as an example of pseudepigraphy and the creative traditions of Hellenistic literary culture.