He graduated in Classics (lettere classiche) from the University of Padua, and became politically active during the years of the Nazi occupation of Italy, and was subsequently a leading member of the Italian Socialist Youth. In 1947 he joined the Fourth International, of which he was a leading member from 1951 throughout his life. In 1948 he was a member of the leadership of the Fronte Democrazia Popolare.
Maitan was one of a small group of colleagues who led the Fourth International during the difficult years of the 1950s and early 1960s. First elected in 1951, he remained a member of the International leadership, reelected at each congress, until his death. Critics of the Fourth International talked about the “Mandel-Frank-Maitan” leadership of the FI, following the departure of Michel Pablo.
His generation were the cadres who continued as revolutionary Marxists through the post-World War II years, and who were gradually able to connect their vision with the young activists in the mid- and late 1960s. Maitan was actively involved in the large-scale student movement in Italy between 1969 and 1976, and widely seen as the main inspiration for leaders of the Italian revolutionary left, whether inside the Fourth International or outside.
In the 1970s he also lectured on the economy of underdevelopment in the School of Sociology at the University of Rome. He translated and introduced almost all the Italian editions of Leon Trotsky’s writings.
In 1989 the Italian Fourth Internationalists organised around Lega Comunista Rivoluzionaria, which joined Democrazia Proletaria, and with DP participated in 1991 in the foundation of the Communist Refoundation Party, PRC. He was elected to the leadership of the PRC at each successive Congress from 1991 until 2002.
Until just before his death, he maintained his participation in all the leadership bodies of the FI. A football fanatic, he played weekly until into his seventies.
There is a long list of his publications in Italian. Translated works include his 1976 book on the Chinese Cultural Revolution and a long text on the history of the Italian Communist Party, published by the International Institute for Research and Education in English and French. In 2002 he wrote "Per una storia della Quarta Internazionale" (Rome, ed. Alegre), history of the Fourth International.
He wrote also for the journals of the Italian Fourth Internationalists (Bandiera Rossa and subsequently ERRE), of Rifondazione (Liberazione) and of the Fourth International, Inprecor and International Viewpoint.
In a late publication (La strada percorsa - "The road taken"), Maitan argued strongly against the view that the defeats of socialism in the 20th Century were "inevitable", and equally strongly for the view that the possibility of Socialism remains open.
In 2007 the Livio Maitan Study Centre was set up in Rome with the support of a large number of academics, including Gilbert Achcar, Daniel Bensaïd, Tariq Ali, Alex Callinicos, Claudio Katz, Michael Löwy and Slavoj Žižek.