Guglielmo Achille Cavellini (11 September 1914 – 20 November 1990), also known as GAC, was an Italian artist and art collector. After an initial activity as a painter, in the 1940s and 1950s he became one of the major collectors of contemporary Italian abstract art, developing a deep relationship of patronage and friendship with the artists. This experience has its pinnacle in the exhibition Modern painters of the Cavellini collection at the National Gallery of Modern Art in Rome in 1957. In the 1960s Cavellini resumed his activity as an artist, with an ample production spanning from Neo-Dada to performance art to mail art, of which he became one of the prime exponents with the Exhibitions at Home and the Round Trip works. In 1971 he invented autostoricizzazione (self-historicization), upo