Jacques Marie Eugène Godefroy Cavaignac (May 21, 1853 - September 25, 1905), French politician, was born in Paris.

He was the son of Louis Eugène Cavaignac. He made public profession of his republican principles as a schoolboy at the Lycée Charlemagne by refusing in 1867 to receive a prize at the Sorbonne from the hand of the prince imperial. He received the military medal for service in the Franco-Prussian War, and in 1872 entered the École Polytechnique. He served as a civil engineer in Angoulême until 18Sf, when he became master of requests in the council of state.

In the next year he was elected deputy for the arrondissement of Saint-Calais (Sarthe) in the republican interest. In 1885-1886 he was under-secretary for war in the Henri Brisson ministry, and he served in the cabinet of Émile Loubet (1892) as minister of marine and of the colonies. He had exchanged his moderate republicanism for radical views before he became war minister in the cabinet of Léon Bourgeois (November 1, 1895 to April 29, 1896).

He was again minister of war in the Brisson cabinet from June 28, 1898 to September 5, 1898. In July 1898, he read in the chamber a document which definitely incriminated Captain Alfred Dreyfus. On August 30, however, he stated that this had been discovered to be a forgery by Colonel Henry , but he refused to concur with his colleagues in a revision of the Dreyfus prosecution, which was the logical outcome of his own exposure of the forgery. Resigning his portfolio, he continued to declare his conviction of Dreyfus's guilt, and joined the Nationalist group in the chamber, of which he became one of the leaders. He also was an energetic supporter of the Ligue de la Patrie Française .

In 1899 Cavaignac was an unsuccessful candidate for the presidency of the republic. He had announced his intention of retiring from political life when he died at his country-seat near Flée (Sarthe) on September 25, 1905.

He wrote an important book on the Formation de la Prusse contemporaine (2 vols., 1891-1898), dealing with the events of 1806-1813.