The Government of National Defense was the first government of the Third Republic of France from 4 September 1870 to 13 February 1871 during the Franco-Prussian War. It was formed after the proclamation of the Republic in Paris on 4 September, which in turn followed the surrender and capture of Emperor Napoleon III by the Prussians at the Battle of Sedan. The government, headed by General Louis Jules Trochu, was under Prussian siege in Paris. Breakouts were attempted twice, but met with disaster and rising dissatisfaction of the public. In late January the government, having further enraged the population of Paris by crushing a revolutionary uprising, surrendered to the Prussians. Two weeks later, it was replaced by the new government of Adolphe Thiers, which soon passed a variety of financial laws in an attempt to pay reparations and thus oblige the Prussians to leave France, leading to the outbreak of revolutions in French cities, and the ultimate creation of the Paris Commune.

The French Third Republic was the system of government adopted in France from 4 September 1870, when the Second French Empire collapsed during the Franco-Prussian War, until 10 July 1940, after the Fall of France during World War II led to the formation of the Vichy government.