Francesco I Sforza (July 23, 1401 – March 8, 1466) was an Italian condottiero, the founder of the Sforza dynasty in Milan, Italy. He was the brother of Alessandro, with whom he often fought.

Francesco Sforza was born in San Miniato, Tuscany, one of the seven illegitimate sons of the condottiero Muzio Sforza and Lucia da Torsano. He spent his childhood in Tricarico (in the modern Basilicata), the marquisate of which he was granted in 1412 by King Ladislaus of Naples. In 1418, he married Polissena Ruffo, a Calabrese noblewoman.

From 1419, he fought alongside his father, soon gaining fame for being able to bend metal bars with his bare hands. He later proved himself to be an expert tactician and very skilled field commander. After the death of his father, he fought initially for the Neapolitan army and then for Pope Martin V and the Duke of Milan, Filippo Maria Visconti. After some successes, he fell in disgrace and was sent to the castle of Mortara as a prisoner de facto. He regained his status after a successful expedition against Lucca.