Stjepan Gradić, also known as Stefano Gradi (Latin: Stephanus Gradius; 6 March 1613 – 2 May 1683)[1] was a polymath,[2] philosopher, scientist and a patrician of the Republic of Ragusa.

He became a priest in 1643, the year he returned home and soon became abbot of the Benedictine abbey of St. Cosmas and Damian on the island of Pašman, canon of cathedral choir in Ragusa and Ragusan deputy Archbishop.

This work went unnoticed and was even unknown to Roger Joseph Boscovich who was a professor of mathematics at the Collegium Romanum where a century before Gradić had been an alumnus.

In his only printed mathematical treatise De loco Galilaei quo punctum lineae aequale pronuntiat published in the collection Dissertationes physico-mathematicae quatuor he disputed the concept of indivisible and developed a series of ideas en route to infinitesimal method.

In scientific correspondence with Giovanni Alfonso Borelli and Honoré Fabri he published works dealing with the natural causes of motion and the laws of acceleration and falling bodies.