Apollonius Dyscolus (fl. 2nd century AD) is considered one of the greatest of the early Greek grammarians. Nicknamed 'dyscolus', meaning 'hard to please', because of his irascible and heavily analytical personality he wrote extensively on the parts of speech. Of twenty books named in the Suda, four survive; on syntax, the adverb, the conjunction, and the pronoun.

Son of Mnesitheus, and a lifelong resident of Alexandria, little more is known of his life.

Although his own work was in fact quite careless he influenced later generations of grammarians including his own son Aelius Herodianus.