Francis Cassidy, QC (17 January 1827 – 14 June 1873) was a Canadian lawyer and politician, the Mayor of Montreal, Quebec for three months in 1873, until his term was cut short by death.

Despite spending childhood in a poor family, he attended Collège de l’Assomption with the support of Abbé Étienne Normandin.

After developing a distinguished legal career, he was designated Queen's Counsel on 5 August 1863.

From 1871 to 1873, he served as a Conservative member for Montréal-Ouest riding during the first portion of the 2nd Legislative Assembly of Quebec.

Just months after becoming Montreal's uncontested mayor in February 1873, Cassidy died in office that June.