Benoît Frachon (French pronunciation: [bənwa fʁaʃɔ̃]; 13 May 1893 – 1 August 1975), a French metalworker and trade union leader, was one of the leaders of the French Communist Party (Parti communiste français, PCF) and of the French Resistance during World War II (1939–45). He was Secretary-General of the Confédération générale du travail (CGT) from 1945 to 1967.

Benoît Frachon was born on 13 May 1893 in Le Chambon-Feugerolles, Loire, the third of five children in a working-class family. Le Chambon-Feugerolles was a mining and industrial town in the Loire coal basin. His father was a miner who died of uremia at the age of 51. Benoît received a Certificate of Primary Education in July 1904. He went on to secondary school in Chambon-Feugerolles, but dropped out two years later. At the age of thirteen he became apprenticed to a former metal worker, who taught him the basic skills.

When Frachon's father died he obtained work with a manufacturer of bolts and other hardware. He joined the union in 1909. He joined a strike at his factory in January 1910 that soon spread to all the metal works in the Loire. He lost his job due to another strike in 1911, but soon found work in a machine factory. He joined a small anarchist group of miners and metalworkers created in 1909, and read Gustave Hervé's weekly La Guerre Sociale and Pierre Monatte's La Vie Ouvrière. He often visited the Maison du Peuple in Chambon, where he participated in theatrical productions and read widely in the library. Frachon joined the general strike in 1912 against the "Three Years Law". In 1913 he was called up for military service. He was placed in the auxiliary service due to his myopia, and was in the clothing store of the 30th Artillery Regiment in Orléans at the outbreak of World War I (1914–18).

Frachon was returned to active duty in the Guérigny naval arsenal, but due to his technical skills was not sent to the front. Frachon disagreed with the CGT position of supporting the Union sacrée, under which no industrial actions were taken during the struggle with Germany, and preferred Alphonse Merrheim's opposition to contributing to the war effort. He was a strong supporter of the October Revolution in Russia in 1917. Frachon was elected when Albert Thomas, the socialist Minister of Armaments, created worker's delegates. In January 1918 he was an alternate delegate for his workshop, and took a clear position against the war. He was moved from Guérigny that month and given various jobs in the aviation industry. He was at Belfort when the armistice was declared in November 1918. He spent a short time with the troops occupying the Rhineland, then was discharged on 19 August 1919.

Frachon returned to Chambon-Feugerolles on 8 September 1919, where he joined the socialist Section Française de l'Internationale Ouvrière (SFIO). He could not find work in the region, so moved to Marseille where he found a job as a metallurgist at the Giraud-Soulay company. He was soon elected a shop steward, and negotiated with the management in two disputes. During this period he abandoned his anarcho-syndicalist views. After the split of the SFIO at the Tours Congress of 25–30 December 1920 he became a member of the local branch of the French Communist Party. He led his whole section into the Communist Party. In June 1921 Frachon returned to Chambon where he found work with the Société anonyme des aciéries et forges de Firminy. He quit this job after refusing to work on making torpedoes. He was rehired and again fired several times, helped by his qualification but still refusing to make weapons.

In 1922 Frachon became secretary of the metal workers union in Chambon. In this role he participated in the founding congress of the Confédération générale du travail unitaire (CGTU) on 26 June – 1 July 1922 in Saint-Étienne. He supported the union joining the Communist International. He ran successfully in the 1922 municipal elections and became deputy mayor of Chambon, but did not find municipal politics interesting and resigned from this office on 25 August 1922. In March–April 1924 he was among the CGTU Communist activists who led a major strike of 20,000 metalworkers in the Foréz region. He was arrested for undermining the freedom of labor, sentenced to four months in prison and fined 200 francs. The strike did much to advance the position of the Communists in the CGTU against the anarcho-syndicalist leadership. In November 1924 Frachon was appointed permanent secretary to the Loire departmental union of the Confédération générale du travail unitaire (CGTU). In March 1925 he organized a conference of all the Loire unions, against the opposition of the CGTU leaders.

Frachon was elected head of Communist cells in the Lyon region (Rhône-Alpes). In 1925 he became secretary of the PCF trade union committee covering the departments of the Rhône, Loire, Saône-et-Loire, Haute-Loire, Ain, Jura, Ardèche, and part of Isère. On 25 April 1925 Frachon married Marie-Louise Péalat, a seamstress from Chambon. Their son, Henri, was born on 7 January 1929. As secretary of the departmental union of the CGTU he was a member of the French delegation to the sixth session of the Executive Committee of the Communist International in Moscow in February–March 1926. On his return he replaced the secretary of the Lyon region of the PCF. At the PCF's Lille Congress in July 1926 he became a member of the Central Committee. He was very active in promoting the party in meetings throughout the region, fighting Trotskyist influences and praising the example of the Soviet Union. Frachon ran unsuccessfully in the national elections in April 1928 as candidate of the Workers and Peasants Bloc for the 3rd district of Lyon.

Frachon attended the PCE national conference in June 1928, where he was designated delegate to the 6th congress of the Communist International in July–September 1928. He returned as an alternate member of the Executive Committee. In November 1928 Maurice Thorez proposed him as a member of the Politburo of the PCE Central Committee. At the end of 1928 Frachon moved permanently from Lyon to Paris. He was made a member of the secretariat established at the 1928 congress, along with Henri Barbé, Pierre Célor and Thorez. Frachon and other PCF leaders were arrested on 24 July 1929 at a meeting held in Villeneuve-Saint-Georges to prepare for the international anti-war demonstrations of 1 August. They were charged with conspiracy against the internal and external security of the state. Frachon was jailed in La Santé Prison, where he wrote several articles under a pseudonym for L'Humanité and La Vie Ouvrière.