He was born in Florence in 1895. He studied at the Academy of Florence, but he trained above all on the works of Corot, Courbet and Cézanne. In 1913, through Ardengo Soffici, he briefly approached futurism and before the pictorial rigor of the twenties and thirties, a brief cubist period alternated with the futurist phase (Landscape, 1914). However, his painting is immediately characterized by a primitivist and archaic base linked above all to a metaphysical image of the popular neighborhoodsof Florence and its inhabitants.
In November 1920 he held his first personal exhibition in Florence.
Until 1929 he collaborated as an illustrator for some newspapers of the fascist era (Il Selvaggio, Il Bargello).
In the period of maturity he dedicated himself to the observation of the humble and to the description of scenes of everyday life: the works of these years can be traced back to a phase of Italian painting that can be defined as post-futurist, characterized by the return to order, where to emerge they are volumes, sharp edges and rich color.
In 1932 a solo show was dedicated to him at Palazzo Ferroni in Florence, followed by numerous other exhibitions in other cities, including Milan, Rome, Venice.
In 1942 he was assigned the chair of painting at the Academy of Florence.
On the occasion of the 1956 Biennale, a large retrospective of his work is set up.
He died in 1957 in Ivrea, while he took care of the preparation of his personal one.
Ottone Rosai is also remembered as a writer: his most significant literary works are: The book of a hooligan (1919) in which he talks about his war experiences, Via Toscanella (1930), Dentro la guerra (1934) and Vecchio Self-portrait (1951) ).