Billaud-Varenne was the son of a lawyer of La Rochelle. After studying at the Universities of Paris and Poitiers, he taught at the Oratorian college at Juilly. In 1785 he was admitted to the bar at Paris, and by 1787 he was writing anonymous tracts attacking the French church and government. He joined the Jacobin Club soon after the outbreak of the French Revolution in 1789.

As a member of the “revolutionary Commune,” he helped plan the popular insurrection that overthrew the monarchy on August 10, 1792. He was elected a deputy to the revolutionary National Convention, which convened on September 21, and, on his motion, the republic was declared the next day. Billaud-Varenne then threw himself into the struggle against the deputies of the moderate Girondin faction. The leading Girondins were expelled from the Convention on June 2, 1793, and the Jacobins took control of the Revolution.

By that time Billaud-Varenne had formed close ties with the Parisian sansculottes (wage earners and shopkeepers), who looked for leadership to the left-wing Jacobins under Jacques Hébert. Billaud-Varenne's Éléments du républicanisme (1793; “Elements of Republicanism”) set forth Hébertist demands such as the redistribution of wealth and guaranteed employment for all workers.

Taking advantage of popular unrest in Paris, the Hébertists forced the Convention to appoint Billaud-Varenne and Jean-Marie Collot d'Herbois (Collot d'Herbois, Jean-Marie) to the Committee of Public Safety (Public Safety, Committee of) on September 6, 1793. On 14 Frimaire, year II (December 4, 1793), Billaud-Varenne secured passage of a law giving the Committee absolute authority over provincial officials. Maximilien Robespierre (Robespierre, Maximilien de), the Committee's chief spokesman, had the leading Hébertists guillotined in March 1794, and in the following month Billaud-Varenne and Collot d'Herbois forced him to eliminate Georges Danton, the leader of the Jacobins' right wing. Soon Billaud-Varenne was challenging Robespierre's leadership. Conspiring with Collot d'Herbois and other dissidents, he helped bring about Robespierre's downfall on 9 Thermidor, year II (July 27, 1794). In the ensuing Thermidorian Reaction against the Jacobin regime, Billaud-Varenne and Collot d'Herbois were deported to French Guiana (April 1795), where Billaud-Varenne married and became a farmer. In 1800 he turned down Napoleon Bonaparte's offer of a pardon. He made his way to New York City in 1816 but settled in Haiti the following year.