John Gaspar Gevartius or Jan Caspar Gevaerts (1593-1666) was the jurisconsult of Antwerp and in his lifetime a famous philologist. He was a personal friend of Peter Paul Rubens.
Gaspar was born in Turnhout on 6 August 1593, the son of Johannes Gevaerts (1553-1613) and Cornelia Aerssens, whose father had been mayor of Bergen op Zoom. He was educated by the Jesuits, going on to study the Liberal Arts at Louvain University. He was briefly in the service of Benjamin Aubery du Maurier, French Ambassador in The Hague, where he became friends with Daniel Heinsius, writing an epithalamium on his marriage. In 1617 he moved to Paris, entering the household of Henri de Mesmes. In 1621 he was granted a law degree by the University of Douai.
After 1621 he became an important functionary of the city government of Antwerp. He wrote works on poetry and sciences, one of which treats of Marcus Aurelius. His reputation was known by the Archduchess Isabella Clara Eugenia and Emperor Ferdinand III.Pierre Gassendi's biography of Nicolas Peiresc mentions that in 1620 he consulted Gevartius, "a famous and (if ever any) a true Schollar", about the Duke of Aarschot's cabinet of curiosities. He was appointed councillor of state and historiographer royal by both Philip IV of Spain and the Emperor Ferdinand III.
On 14 May 1625 Gevartius married Marie Haecx in the church of St James in Antwerp. Their son died at the age of 12; their daughter married Charles Sivori, whose father, Anthonie Sivori, served eleven terms as mayor of Antwerp.