Lorenzo Magalotti was born on October 24, 1637, in Rome to a Florentine aristocratic family. He is the son of Orazio Magalotti, Prefect of the Pontifical Mail and Francesca Venturi. His uncle Lorenzo Magalotti was a member of the Roman Curia and the cousin of Urban VIII and one of Urban's most trusted advisers. His cousin Filippo was rector at the University of Pisa. Orazio Magalotti, wealthy by inheritance, was a spendthrift. He went to Rome (where Lorenzo was born) with Urban to maintain his diminishing fortune, which he did. He was named to the Roman nobility and was employed, inter alia, as a papal ambassador. Despite the father's prodigality, one has to say that Lorenzo grew up in wealthy circumstances.
It is difficult to figure, from the existing literature, how extensive the estate that Magalotti inherited was. His extravagant father was frequently more of a burden than anything else. In 1679 Magalotti also inherited something (which he found to be too little) from a brother. He owned two estates from which he received rents. He had (the time is around 1695) 47,000 scudi in the land, from which he received a net income of only 600 scudi.