Pierre Gassendi (; also
Pierre Gassend,
Petrus Gassendi; 22 January 1592 – 24 October 1655) was a
French philosopher,
priest,
scientist,
astronomer, and
mathematician. While he held a church position in south-east France, he also spent much time in Paris, where he was a leader of a group of free-thinking intellectuals. He was also an active observational scientist, publishing the first data on the
transit of Mercury in 1631. The lunar crater
Gassendi is named after him.