Little is known about Leonardo's early life. He spent his first five years in the hamlet of Anchiano in the home of his mother, and from 1457 lived in the household of his father, grandparents and uncle in the small town of Vinci. His father had married a sixteen-year-old girl named Albiera Amadori, who loved Leonardo but died young in 1465 without children. When Leonardo was sixteen (1468), his father married again to twenty-year-old Francesca Lanfredini, who also died without children. Piero's legitimate heirs were born from his third wife Margherita di Guglielmo (who gave birth to six children: Antonio, Giulian, Maddalena, Lorenzo, Violante and Domenico) and his fourth and final wife, Lucrezia Cortigiani (who bore him another six children: Margherita, Benedetto, Pandolfo, Guglielmo, Bartolomeo and Giovanni).

In all, Leonardo had twelve half-siblings, who were much younger than him (the last was born when Leonardo was forty years old) and with whom he had very few contacts, but they caused him difficulty after his father's death in the dispute over the inheritance.

Leonardo received an informal education in Latin, geometry and mathematics. In later life, Leonardo recorded only two childhood incidents. One, which he regarded as an omen, was when a kite dropped from the sky and hovered over his cradle, its tail feathers brushing his face. The second occurred while he was exploring in the mountains: he discovered a cave and was both terrified that some great monster might lurk there and driven by curiosity to find out what was inside.