Francesco Cetti SJ (9 August 1726 – 20 November 1778) was an Italian Jesuit priest, zoologist and mathematician.

He entered the Jesuit novitiate in Milan on 12 October 1742, and professed the four vows on 2 February 1760.

He devoted himself to scientific studies and taught for several years philosophy and mathematics at the Jesuit College of Brera, soon becoming one of the most prominent members of the Milanese province.

In 1766 he was appointed to the Chair of Mathematics at the University of Sassari, holding that position until his death.

Cetti took long excursions in the vicinity of Sassari, collating his discoveries in the Storia Naturale di Sardegna (Natural History of Sardinia, 1774–7).