The Letters of Anaximenes of Miletus are a 4th-century BCE work, though not authored by the famous 6th-century BCE philosopher of the same name. The historical Anaximenes was a pre-Socratic thinker from Miletus known for positing air as the fundamental substance of the cosmos. The letters are a later pseudepigraphic creation, 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 demonstrate how later generations used the names of early thinkers to create ethical or biographical scenarios, reflecting Anaximenes' lasting reputation rather than providing factual information about him. The work is therefore studied as an example of pseudepigraphy and the creative traditions of Hellenistic literary culture.