Cesare Viazzi was an Italian painter.

Born in Alessandria, he was initially a student of the sculptor and architect Angelo Cavanna in Novi Ligure. He then became a pupil of Andrea Gastaldi, first in Rome then at the Accademia Albertina in Turin. In 1893, he was named professor of the Accademia Ligustica di Belle Arti in Genoa. Among his pupils was Pietro Gaudenzi.

In Genoa, he was known for his portraits, but also completed large fresco or decorative cycles, including for the Società promotrice di Belle Arti, Palazzo Raggio in via Balbi, Castello Raggio a Cornigliano, Villa Weil, and the Villa Bisio in Albaro. He painted sacred subjects for chapels in the Monumental Cemetery of Staglieno.

At the 1883 Exposition of Rome, he exhibited a canvas of Il Beccaio. In the 1884 Turin, exhibition, he displayed: La vanità nei campi; Fiori di biancospino; La Scrivia; Il giorno di San Bovo; Ore calde. In 1887, in Venice: Un pescatore sul lago; Idillio; Mar. In 1888, in Bologna: Autunno mesto; Fede; Fiori. Among other works Il Canto del mattino and Ritorno dai campi

He died in Predosa in 1943.