Didymus Chalcenterus was a Greek scholar and grammarian who lived and worked in Alexandria during the late 1st century BCE and early 1st century CE, a period of transition from Ptolemaic to Roman rule. His nickname, "Chalcenterus," meaning "with guts of bronze," reflected his legendary productivity. He was a student of the famous grammarian Aristarchus of Samothrace and belonged to the Alexandrian tradition of textual criticism.

His scholarly output was enormous. Ancient records claim he wrote between 3,500 and 4,000 books, a number considered exaggerated but indicative of his vast work. He wrote critical commentaries on a wide range of Greek authors, including Homer, the lyric poets like Pindar, dramatists such as Sophocles and Aristophanes, and the orator Demosthenes. He also produced lexicographical works on topics like ambiguous words. Almost none of his writings survive intact; they are known only through fragments found in later ancient commentaries, notes (scholia), and papyri.

According to modern scholars, Didymus's primary importance lies in his role as a preserver and compiler. His work systematically gathered and evaluated the textual criticisms and interpretations of earlier Alexandrian scholars, especially those of his teacher Aristarchus. These compiled commentaries became standard reference tools for later generations. While some ancient critics viewed his focus on minute details as pedantic, his encyclopedic efforts were crucial for transmitting and stabilizing the texts of major Greek authors through the Roman and into the Byzantine era.