Francesco Maidalchini (21 April 1631 – 13 June 1700) was an Italian Cardinal of the Roman Catholic Church.
Maidalchini was born 12 April 1631 in Viterbo, the son of Andrea Maidalchini and Pacifica Feliziani. His father was the brother of Olimpia Maidalchini; sister-in-law of Pope Innocent X. Anti-Catholic publicist Gregorio Leti described Francesco Maidalchini as a person "with no experience in the things of the world, ignorant in letters and incapable of learning".
He was named commendatory abbot of St. Martin and St. Gaudentius of Rimini and San Pancrazio outside the walls of Rome. He also received the title of Canon of St. Peter's Basilica in Rome.
In 1647, Maidalchini's first counsin, Camillo Francesco Maria Pamphili, resigned his post as Cardinal-Nephew to marry and Innocent X required a new Cardinal Nephew. Without any remaining male relative to turn to for an assistant, Innocent X was persuaded to appointed the seventeen year old Francesco, his sister-in-law's nephew. Upon being elevated to Cardinal, he was installed as Cardinal-Deacon of Sant'Adriano al Foro. Many of the responsibilities of the Cardinal-nephew had been previously delegated to the Secretary of State, Cardinal Giovanni Giacomo Panciroli, with the military duties assigned to the husbands of the Pope's two nieces. It is possible that the pontiff meant simply to install a relative, however distant, in the Sacred College, without this implying an effective delegation of powers. Without adequate political knowledge for the role, Francesco was assisted by Cardinals Panciroli and Domenico Cecchini, but he nonetheless remained in a substantially weak political position. The Pope's sisters and other members of the Pamphilj family begrudged his close association with the pontiff and shunned the "adopted" nephew.
Girolamo Gigli wrote that Francesco's paternal aunt, Olimpia required him to reside with her at the Palazzo Pamphili in Piazza Navona rather than in the papal palaces, so as "not to lose her dominion", and to prevent his making independent decisions. However it was immediately clear that the new Cardinal-nephew would not have enjoyed any real power. Innocent X continued to entrust the politically relevant affairs to Secretary of State Cardinal Panciroli. During his brief tenure as Cardinal-nephew, Cardinal Maidalchini was universally evaluated in a negative way by diplomatic observers, who saw in some of his misguided initiatives the hand of his aunt.