Pietro La Fontaine (29 November 1860 – 9 July 1935) was an Italian Roman Catholic cardinal who served as the Patriarch of Venice from 1915 until his death.

[2] His father was from Geneva in origins and had been a soldier in the papal guard turned watchmaker while his mother was the daughter of Giuseppe Bianchini who served as the administrator general of the properties of the Doria-Pamphili-Landi.

Pope Pius X appointed him as the Bishop of Cassano all'Jonio and he received his episcopal consecration on 23 December 1906 in Rome at the Collegio Capranica chapel from Pietro Respighi with Antonio Maria Grasselli and Raffaele Virili serving as the co-consecrators.

[1] On 28 December 1908 an earthquake that had struck Messina and surrounding cities saw him open the doors to the episcopal palace for people to find refuge.

He spent the entire night begging for relief from the Mother of God and vowed he would build a temple in her honor if Venice was spared from further bombings.

La Fontaine participated in the papal conclave of 1922 that elected Pope Pius XI, and was himself viewed as "papabile" for his pastoral qualities.

The German cardinals met just after the conclave opened before retiring for the evening, after having deliberated and settling on voting for La Fontaine as their second choice if Pietro Gasparri withdrew his candidature.

[2] He was frugal in his outlook and before he died sold his gondola, hoping the funds collected would be used for the poor, while eschewing heating in the patriarchal palace during the cold winter months.

His remains were transferred on 8 July 1959 into the Basilica of Saint Mark in the sarcophagus that was once intended for his future successor Angelo Giuseppe Roncalli, who had become Pope John XXIII.