in Argentine politics, a supporter of Juan Perón (Perón, Juan), a member of the Justicialist Party (Spanish Partido Justicialista), or an adherent of the populist and nationalistic policies that Perón espoused. Peronism has played an important part in Argentina's history since the mid-1940s.

The Peronist movement arose as the personal following of Colonel Juan Perón. In 1943, after participating in a successful military coup, Perón became Argentina's minister of labour, a position through which he enacted various social measures to help the country's growing class of urban industrial workers. Gaining the admiration of the masses, Perón called for the state to take a leading role in the economy to ensure cooperation between businesses and labour. In 1946 he was elected to the presidency with the strong support of the workers and their labour unions; he also gained the support of many lower-middle-class citizens and of the country's industrialists. After Perón was overthrown and exiled in 1955 by the military, the leaderless Peronist movement was weakened by factional conflicts, since it was composed of many divergent elements, from left-wing trade unionists to right-wing authoritarian nationalists. Nonetheless, the movement remained the main civilian contender for power in Argentina.

Under the new name of the Justicialist Nationalist Movement (later the Justicialist Party), the Peronists swept back into power in 1973 when the military permitted the first general elections in 10 years. Perón returned from exile and became president. However, deep dissension between right-wing and left-wing Peronists erupted into terrorism and violence after Perón's death in 1974, and the military overthrew Perón's widow and successor as president, Isabel (Perón, Isabel), in 1976. The Peronists lost the presidential election of 1983, but in 1989 their candidate, Carlos Saúl Menem (Menem, Carlos), was elected to the presidency. Breaking with traditional Peronist policies, Menem implemented free-market-oriented policies, which expanded the party's base to include the wealthy and business classes. In 1999 the Peronists lost the presidency, but after massive rioting forced the resignation of President Fernando de la Rúa in 2001, the Peronists recaptured the office.