Louis Billot (12 January 1846 in Sierck-les-Bains, Moselle, France – 18 December 1931 in Ariccia, Latium, Italy) was a French Jesuit priest and theologian.

[1] While largely unknown in the modern age, he was nonetheless considered "the most important Thomistic speculative theologian of the late nineteenth century.

Billot's support for the deeply conservative movement Action Française eventually created tension between him and the Holy See.

Billot expressed strong disagreement with the decision, saying that the political activities of monarchist Catholics ought not to be censured by Rome.

[7] On 13 September 1927, in a meeting with Pope Pius XI, Billot submitted a letter asking to be allowed to resign as cardinal.

The Pope announced Billot's change in status to the College of Cardinals at the consistory on 19 December, saying: "The autograph letter with which he tendered his resignation adduced such high spiritual motives, and in such grave circumstances, that after much thought and prayer we decided to accept them.