Claudio Achillini (September 18, 1574 – October 1, 1640) was an Italian philosopher, theologian, mathematician, poet, and jurist.

Born in Bologna, he was grandson to Giovanni Filoteo Achillini and grand nephew to Alessandro Achillini. He was professor of jurisprudence for several years at his native Bologna, Parma, and Ferrara, with the highest reputation. So much admiration did his learning excite, that inscriptions to his honor were placed in the schools in his lifetime.

Achillini went to Rome, where he obtained great promises of preferment from popes and cardinals, but they proved only promises. Odoardo Farnese, duke of Parma, engaged him however on very liberal terms, to occupy the chair of law in his university. Achillini was a particular friend of Giambattista Marino, whose style in poetry he imitated, adopting the same strain of turgid metaphors, absurd thoughts, and points, which obtained the applause of that age. A canzone, which he addressed to Louis XII on the birth of the dauphin, is said to have been rewarded by Cardinal Richelieu with a gold chain or collar worth 1000 crowns; this reward was not given, as some have asserted, for the famous sonnet beginning, "Sudate o fuochi, a preparar metalli;" and which was parodied by Crudeli in one beginning, "Sudate o forni, a preparar pagnotte," (Sweat, O ye ovens! in preparing cakes!)

Achillini's poems were published at Bologna in 1632. He also printed a volume of Latin letters.