Fouché was born in Le Pellerin, a small village near Nantes. His mother was Marie Françoise Croizet (1720 - 1793), and his father was Julien Joseph Fouché (1719 - 1771). He was educated at the college of the Oratorians at Nantes, and showed aptitude for literary and scientific studies. Wanting to become a teacher, he was sent to an institution kept by brethren of the same order in Paris. There he made rapid progress, and was soon appointed to tutorial duties at the colleges of Niort, Saumur, Vendôme, Juilly and Arras. At Arras he had had some encounters with Maximilien Robespierre both before the revolution and in the early days of the French Revolution (1789).

In October 1790, he was transferred by the Oratorians to their college at Nantes, in an attempt to control his advocacy of revolutionary principles - however, Fouché became even more of a democrat. His talents and anti-clericalism brought him into favour with the population of Nantes, especially after he became a leading member of the local Jacobin Club. When the college of the Oratorians was dissolved in May 1792, Fouché gave up the church, whose major vows he had not taken.

After the downfall of the monarchy on 10 August 1792 (following the storming of the royal Tuileries Palace), he was elected as deputy for the départment of the Loire-Inférieure to the National Convention — which met on 22 September and proclaimed the French Republic.

Fouché's interests brought him into contact with the Marquis de Condorcet and the Girondists, and he became a Girondist himself. However, their lack of support for the trial and execution of King Louis XVI (December 1792 - 21 January 1793) led him to join the Jacobins, the more decided partisans of revolutionary doctrine. Fouché was strongly in favor of the king's immediate execution, and denounced those who wavered.

The crisis which resulted from the declaration of war by the Convention against Great Britain and the Dutch Republic (1 February 1793), and a little later against Spain, made Fouché famous as one of the Jacobin radicals holding power in Paris. While the armies of the First Coalition threatened the north-east of France, a revolt of the Royalist peasants in Brittany and La Vendée menaced the Convention on the west. That body sent Fouché with a colleague, Villers, as representatives on mission invested with almost dictatorial powers for the crushing of the revolt of "the whites" (the royalist colour). The vigour with which he carried out these duties earned him a reputation, and he soon held the post of commissioner of the republic in the département of the Nièvre.

Together with Pierre Gaspard Chaumette, he helped to initiate the dechristianization (a term first coined by its enemies) movement in the autumn of 1793. In the Nièvre department, Fouché ransacked churches, sent their valuables to the treasury, and helped established the Cult of Reason. He ordered the words "Death is an eternal sleep" to be inscribed over the gates to cemeteries. He also fought luxury and wealth, wanting to abolish the use of currency. The new cult was inaugurated at Notre Dame de Paris by "The Festival of Reason". It was here that Fouché gave “the most famous example of its [dechristianization] early phase." Ironically enough, it was only a year previous that Fouché had been "an advocate of the role of the clergy in education," yet he was now "abandoning the role of religion in society altogether in favour of 'the revolutionary and clearly philosophical spirit' he had first wanted for education." Overall, the dechristianization movement "reflected the wholesale transformation that Jacobin and radical leaders were beginning to see as necessary for the survival of the Republic, and the creation of a republican citizenry."

Fouché went on to Lyon in November with Jean-Marie Collot d'Herbois to execute the reprisals of the Convention. Lyon had revolted against the Convention and needed to be dealt with. Lyon, on 23 November, was declared to be in a "state of revolutionary war" by Collot and Fouché. The two men then formed the Temporary Commission for Republican Surveillance. He inaugurated his mission with a festival notable for its obscene parody of religious rites. Fouché and Collot then brought in "a contingent of almost two thousand of the Parisian Revolutionary Army" to begin their terrorizing. "On 4 December, 60 men, chained together, were blasted with grapeshot on the paline de Brotteaux outside the city, and 211 more the following day. Grotesquely ineffective, these mitraillades resulted in heaps of mutilated, screaming, half-dead victims, who had to be finished off with sabres and musket fire by soldiers physically sicked at the task." It is through events like this that made Fouché infamous as "The Executioner of Lyons." The Commission was not happy with the methods used for killing the rebels, so soon after this "more normal firing squads supplemented the guillotine." These methods led to the carrying out of "over 1800 executions in the coming months." Fouché, claiming that "Terror, salutary terror, is now the order of the day here.... We are causing much impure blood to flow, but it is our duty to do so, it is for humanity's sake," called for the execution of 1,905 citizens. As Napoleon's biographer Alan Schom has written:

Alas, Fouché's enthusiasm had proved a little too effective, for when the blood from the mass executions in the center of Lyons gushed from severed heads and bodies into the streets, drenching the gutters of the Rue Lafont, the vile-smelling red flow nauseated the local residents, who irately complained to Fouché and demanded payment for damages. Fouché, sensitive to their outcry, obliged them by ordering the executions moved out of the city to the Brotteaux field, along the Rhône.

From late 1793 into spring, 1794, every day "batch after batch of bankers, scholars, aristocrats, priests, nuns, and wealthy merchants and their wives, mistresses, and children" were taken from the city jails to Brotteaux field, tied to stakes, and dispatched by firing squads or mobs. Modern research, however, demonstrates that at the close of those horrors Fouché exercised a moderating influence. Outwardly, his conduct was marked by the utmost rigour, and on his return to Paris early in April 1794, he thus characterised his policy: "The blood of criminals fertilises the soil of liberty and establishes power on sure foundations".

By that time Maximilien Robespierre, who was the de facto dictator of revolutionary France through his domination of the Assembly by his control over the organs of the Terror: the Committee for Public Safety and the Revolutionary Tribunal, stuck down one by one the other prominent leaders of the revolution of both the right, (the Rolands and the Girondists), the ultra left, (Jacques Hébert and the Herbertists), and the moderates (Georges Danton and his associates). However, early in June 1794, at the time of his "Festival of the Supreme Being", Fouché ventured to mock the theistic revival which Robespierre then inaugurated. A sharp exchange took place between them, and Robespierre tried to expel Fouché from the Jacobin Club on 14 July 1794. At the time expulsion from the club was tantamount to a death sentence. Fouché, however, was working with his usual energy and plotted Robespierre's overthrow from behind the scenes while in hiding in Paris. Because Robespierre was losing his influence, and because Fouché was under the protection of Barras, he ultimately survived this expulsion.

Remaining ultraleftists (Collot, Billaud) and moderates (Bourdon, Fréron), winning the support of the nonaligned majority of the Convention (Marais), also opposed to Robespierre's reign. Fouché engineered Robespierre's overthrow, culminating in the dramatic Coup of the 9th Thermidor on 28 July 1794. Fouché is reported to have worked furiously on the overthrow: 'Rising at early morn he would run round till night calling on deputies of all shades of opinion, saying to each and every one, "You perish tomorrow if he [Robespierre] does not".' Fouché describes his activities in this way in his memoirs:

"Being recalled to Paris, I dared to call upon [Robespierre] from the tribune, to make good his accusation. He caused me to be expelled from the Jacobins, of whom he was the high-priest; this was for me equivalent to a decree of proscription. I did not trifle in contending for my head, nor in long and secret deliberations with such of my colleagues as were threatened with my own fate. I merely said to them... 'You are on the list, you are on the list as well as myself; I am certain of it!'"

Fouché, as both a ruthless suppressor of Federalist rebellion and one of the proponents of Robespierre's overthrow, demonstrated the mercilessness that politics took on in France during the de-Christianization period. Fouché was a dangerous critic of Robespierre, and his influence undoubtedly contributed to Robespierre's apparent nervous breakdown, which loosened his hold on Parisian politics and the Convention, and ultimately led to his overthrow and execution.

The ensuing movement in favour of more merciful methods of government threatened to sweep away the group of politicians who had been mainly instrumental in carrying through the coup d'état. Nonetheless, largely because of Fouché's intrigues, they remained in power for a time after July. This also brought divisions in the Thermidor group, which soon became almost isolated, with Fouché spending all his energy on countering the attacks of the moderates. He was himself denounced by François Antoine de Boissy d'Anglas on 9 August 1795, which caused his arrest, but the Royalist rebellion of 13 Vendémiaire Year IV aborted his execution, and he was released in the amnesty which followed the proclamation of the Constitution of 5 Fructidor.

In the ensuing Directory government (1795 - 1799), Fouché remained at first in obscurity, but the relations he had with the far left, once headed by Chaumette and now by François-Noël Babeuf, helped him to rise once more. He is said to have betrayed to the Director Paul Barras Babeuf's plot of 1796, however, recent research has tended to throw doubt on the assertion.

His rise from poverty was slow, but in 1797 he gained an appointment dealing with military supplies, which offered considerable opportunities for making money. After first offering his services to the Royalists, whose movement was then gathering force, he again decided to support the Jacobins and Barras. In Pierre François Charles Augereau's anti-Royalist coup d'état of Fructidor 1797, Fouché offered his services to Barras, who in 1798 appointed him French ambassador to the Cisalpine Republic. In Milan, he was judged so high-handed that he was removed, but he was able for a time to hold his own and to intrigue successfully against his successor.

Early in 1799, he returned to Paris, and after a brief stint as ambassador at The Hague, he became minister of police at Paris on 20 July 1799. The newly elected director, Emmanuel-Joseph Sieyès, wanted to curb the excesses of the Jacobins, who had recently reopened their club. Fouché closed the Jacobin Club in a daring manner, hunting down those pamphleteers and editors, whether Jacobins or Royalists, who were influential critics of the government, so that at the time of the return of general Napoleon Bonaparte from the Egyptian campaign (October 1799), the ex-Jacobin was one of the most powerful men in France.

Knowing the unpopularity of the Directors, Fouché joined Bonaparte and Sieyès, who were plotting the Directory's overthrow. His activity in furthering the 18 Brumaire coup (November 9-10, 1799), ensured him the favor of Bonaparte, who kept him in office.

In the ensuing French Consulate (1799 - 1804), Fouché efficiently countered the opposition to Bonaparte. Fouché was careful to temper Napoleon's more arbitrary actions, which at times won him the gratitude even of the royalists. While exposing an unrealistic intrigue in which the duchesse de Guiche was the chief agent, Fouché took care that she should escape. Equally skilful was his action in the so-called Aréna-Ceracchi plot, in which agents provocateurs of the police were believed to have played a sinister part. The chief "conspirators" were easily ensnared and were executed when the Plot of the Rue Saint-Nicaise (December 1800) enabled Bonaparte to act with rigour. This far more serious attempt (in which conspirators exploded a bomb near the First Consul's carriage with results disastrous to the bystanders) was soon seen by Fouché as the work of Royalists. When Napoleon showed himself eager to blame the still powerful Jacobins, Fouché firmly declared that he would not only assert but would prove that the outrage was the work of Royalists. However, his efforts failed to avert the Bonaparte-led repression of the leading Jacobins.

In other matters (especially in that known as the Plot of the Placards in the spring of 1802), Fouché was thought to have saved the Jacobins from the vengeance of the Consulate, and Bonaparte decided to rid himself of a man who had too much power to be desirable as a subordinate. On the proclamation of Bonaparte as First Consul for life (1 August 1802) Fouché was deprived of his office, a blow softened by the suppression of the ministry of police and by the attribution of most of its duties to an extended Ministry of Justice.

Fouché became a senator, and received half of the reserve funds of the police which had accumulated during his tenure of office. He continued, however, to intrigue through his spies, who tended to have more information than that of the new minister of police, and competed successfully for the favor of Napoleon at the time of the Georges Cadoudal-Charles Pichegru conspiracy (February - March 1804), becoming instrumental in the arrest of the Duc d'Enghien. Fouché would later say of Enghien's subsequent execution, "It was worse than a crime; it was a mistake." (a statement frequently also attributed to Charles Maurice de Talleyrand-Périgord).

After the proclamation of the First French Empire, Fouché again became head of the re-constituted ministry of police (July 1804), and later of Internal Affairs, with activities as important as those carried out under the Consulate. His police agents were ubiquitous, and the terror which Napoleon and Fouché inspired partly accounts for the absence of conspiracies after 1804. After the Battle of Austerlitz (December 1805), Fouché uttered the famous words: "Sire, Austerlitz has shattered the old aristocracy; the Faubourg Saint-Germain no longer conspires".

Nevertheless, Napoleon did retain feelings of distrust, or even of fear, towards Fouché, as was proven by his conduct in the early days of 1808. While engaged in the campaign of Spain, the emperor heard rumours that Fouché and Charles Maurice de Talleyrand, once bitter enemies, were having meetings in Paris during which Joachim Murat, King of Naples, had been approached. At once he hurried to Paris, but found nothing to incriminate Fouché. In that year Fouché received the title of Duke of Otranto, which Bonaparte created - under the French name Otrante - a duché grand-fief (a rare, hereditary, but nominal honor) in the satellite Kingdom of Naples.

When, during the absence of Napoleon in the Austrian campaign of 1809, the British Walcheren expedition threatened the safety of Antwerp, Fouché issued an order to the préfet of the northern départments of the Empire for the mobilization of 60,000 National Guards, adding to the order this statement: "Let us prove to Europe that although the genius of Napoleon can throw lustre on France, his presence is not necessary to enable us to repulse the enemy". The emperor's approval of the measure was no less marked than his disapproval of Fouché's words.

The next months brought further friction between emperor and minister. The latter, knowing Napoleon's desire for peace at the close of 1809, undertook to make secret overtures to the British cabinet of Spencer Perceval. Napoleon opened negotiations only to find that Fouché had forestalled him. His rage against his minister was extreme, and on 3 June 1810 he dismissed him from his office. However, Napoleon never completely disgraced a man who might again be useful, and Fouché received the governorship of the Rome département. At the moment of his departure, Fouché took the risk of not surrendering to Napoleon all of certain important documents of his former ministry (falsely declaring that some had been destroyed); the emperor's anger was renewed, and Fouché, on learning of this after his arrival to Florence, prepared to sail to the United States. Compelled by the weather and sickness to put back into port, he found a mediator in Elisa Bonaparte, Grand Duchess of Tuscany, thanks to whom he was allowed to settle in Aix-en-Provence and finally to return to his domain of Point Carré. In 1812 he attempted in vain to turn Napoleon from the projected invasion of Russia, and on the return of the emperor in haste from Smarhoń to Paris at the close of that year, the ex-minister of police was suspected of involvement in the conspiracy of Claude François de Malet, which had been unexpectedly successful.

Fouché cleared his name and gave the emperor useful advice concerning internal affairs and the diplomatic situation. Nevertheless, the emperor, still distrustful, ordered him to undertake the government of the Illyrian provinces. On the break-up of the Napoleonic system in Germany (October 1813), Fouché was ordered on missions to Rome and thence to Naples, in order to watch the movements of Joachim Murat. Before Fouché arrived in Naples, Murat invaded the Roman territory, whereupon Fouché received orders to return to France. He arrived in Paris on 10 April 1814 at the time when Napoleon was being constrained by his marshals to abdicate.

Fouché's conduct in this crisis was characteristic. As senator he advised the Senate to send a deputation to Charles, comte d'Artois, brother of Louis XVIII, with a view to a reconciliation between the monarchy and the nation. A little later he addressed to Napoleon, then in de facto banishment on Elba, a letter begging him in the interests of peace and of France to withdraw to the United States. To the new sovereign Louis XVIII he sent an appeal in favour of liberty, and recommending the adoption of measures which would conciliate all interests. The response was unsatisfactory, and when he found that there were no hopes of advancement, he entered into relations with conspirators who sought the overthrow of the Bourbons. The Marquis de Lafayette and Louis Nicolas Davout were involved in the issuer, but their refusal to take the course desired by Fouché and others led to nothing being done. Soon Napoleon escaped from Elba and made his way in triumph to Paris. Shortly before his arrival in Paris (19 March 1815), Louis XVIII sent Fouché an offer of the ministry of police, which he declined: "It is too late; the only plan to adopt is to retreat".

He then foiled an attempt by Royalists to arrest him, and on the arrival of Napoleon he received for the third time the portfolio of police. That, however, did not prevent him from entering into secret relations with the Austrian statesman Klemens Wenzel von Metternich in Vienna, his aim being to prepare for all eventualities. Meanwhile he used all his powers to induce the emperor to democratize his rule, and he is said to have caused the insertion of the words: "the sovereignty resides in the people — it is the source of power" in the declaration of the Conseil d'État. But the autocratic tendencies of Napoleon could not be overridden, and Fouché, seeing the fall of the emperor to be imminent, took measures to expedite it and secure his own interests.

In 1814, Fouché had joined the invading allies and conspired against Napoleon. However, he joined Napoléon again during his return and was police minister during the latter's short-lived reign (Hundred Days). After Napoléon's ultimate defeat (Battle of Waterloo), Fouché again started plotting against his master and joined the opposition of the parliament (after the defeat of Waterloo) and headed the provisional government and tried to negotiate with the allies. He probably also aimed at establishing a republic with himself as head of state. These plans were never realised, and the Bourbons regained power (July 1815). And again, Fouché's services were necessary: as Talleyrand, another notorious intrigant, became the prime minister of the Kingdom of France, Fouché was named his minister of police: so he was a minister of King Louis XVIII, the brother of Louis XVI.

Ironically, Fouché had voted for the death sentence on Louis XVI. Thus, he belonged to the regicides, and ultra-royalists both within the cabinet and outside could hardly tolerate him as a member of the royal cabinet. Fouché, once a revolutionary using extreme terror against the Bourbon supporters, now initiated a campaign of White Terror against real and imaginary enemies of the Royalist restoration (officially directed against those who had plotted and supported Napoléon's return to power). Even Prime Minister Talleyrand disapproved of such practices, including the useless death sentence on Ney and compiling proscription lists of other military people and former republican politicians. Famous (or rather infamous), is the conversation between Fouché and (also proscribed) Lazare Carnot, who had been interior minister during the hundred days' period:

• Carnot: Where should I go then, traitor?
• Fouché: Go where you want, imbecile!

Fouché was soon moved, in fact dismissed, to the post of French ambassador in Saxony; Talleyrand himself lost his portfolio soon after (he was PM from 9 July to 26 September 1815). In 1816 the royalist authorities found Fouché's further services useless, and he was proscribed. He died in exile in Trieste in 1820.

The 1911 Britannica portrays Fouché in the following manner:

"Marked at the outset by fanaticism, which, though cruel, was at least conscientious, Fouché's character deteriorated in and after the year 1794 into one of calculating cunning. The transition represented all that was worst in the life of France during the period of the Revolution and Empire. In Fouché the enthusiasm of the earlier period appeared as a cold, selfish and remorseless fanaticism; in him the bureaucracy of the period 1795 - 1799 and the autocracy of Napoleon found their ablest instrument.

Yet his intellectual pride prevented him sinking to the level of a mere tool. His relations to Napoleon were marked by a certain aloofness. He multiplied the means of resistance even to that irresistible autocrat, so that though removed from office, he was never wholly disgraced. Despised by all for his tergiversations, he nevertheless was sought by all on account of his cleverness. He repaid the contempt of his superiors and the adulation of his inferiors by a mask of impenetrable reserve or scorn. He sought for power and neglected no means to make himself serviceable to the party whose success appeared to be imminent. Yet, while appearing to be the servant of the victors, present or prospective, he never gave himself to any one party. In this versatility he resembles Talleyrand, of whom he was a coarse replica. Both professed, under all their shifts and turns, to be desirous of serving France. Talleyrand certainly did so in the sphere of diplomacy; Fouché may occasionally have done so in the sphere of intrigue." A quintessential political opportunist, Joseph Fouche served many masters, all with the same unconditional devotion. His life and political career give meaning to the aphorism “the end justifies the means”. His name remains synonym of sinuous political maneuvering and unscrupulous betrayal.