Thomas of Erfurt (fl. c. 1300) was a German philosopher, the most important of the so-called Modistae. He was probably a native of Erfurt. He had some connection to the University of Paris as a teacher or student. He later taught at St Severus' Church and the Schottenkirche in Erfurt.^[1]

Thomas wrote at least six works.^[1] His major work, Tractatus de modis significandi seu Grammatica speculativa, was often misattributed to John Duns Scotus until 1922.^[2] All the early manuscript evidence supports its attribution to Thomas. It was written before 1310. Attributed to Scotus, it was one of the subjects of Martin Heidegger's 1916 doctoral thesis.^[1] Charles Sanders Peirce borrowed the name of the first branch of his system of logic, "speculative grammar", from Thomas.^[3] The Grammatica speculativa has been published with English translation and commentary by Godfrey Bursill-Hall (Longman, 1972).

Thomas' other works include commentaries on Porphyry's Isagoge, Aristotle's Categories and On Interpretation, and the anonymous Liber sex principiorum. He also wrote a pedagogical poem on grammar, Commentarius in carmen ‘Fundamentum puerorum’.^[1]