Lelio Falconieri (1585 – 14 December 1648) was an Italian Catholic Cardinal.
Falconieri was born in 1585 in Florence, the tenth of the thirteen children of Paolo Falconieri and his second wife Maddalena degli Albizzi. He was the brother of Don Orazio Falconieri who purchased the Villa Falconieri and commissioned Francesco Borromini to renovate it. Orazio later commissioned Borromini to renovate the church of San Giovanni dei Fiorentini to build a Falconieri family chapel for the burial of the two brothers. He was educated at the University of Perugia and received a doctorate of law.
At a young age he went to Rome and became an advocate at the Roman Curia and papal prelate during the pontificate of Pope Paul V. In 1619 he became Governor of San Severino and a referendary of the Tribunals of the Apostolic Signatura of Justice and of Grace. He became Governor of Spoleto (1621), Vice-governor of Benevento (1622) and Governor of the Campagne and Maritime Province (1622).
Maffeo Barberini was elected Pope Urban VIII at the Papal conclave of 1623 and during his pontificate, Falconieri became the relator of the Sacred Consulta and commissary general of Umbria and Romagna. In 1634 he was elected Titular Archbishop of Tebe and was consecrated in December of that year at the church of San Giovanni dei Fiorentini by Cardinal Giulio Cesare Sacchetti, brother of his sister-in-law Ottavia Sacchetti. Between 1635 and 1637 he was named nuncio to Flanders but returned to Rome due to illness.