Sadamasa Motonaga (1922 Mie Prefecture – 2011 Kobe, Japan) was an self-taught artist and member of the Gutai group.
He graduated from Mie Prefecture Ueno Commercial School in 1938 and started painting figural and landscape works on canvas.
When in 1952 he moved to Kobe and he started to make abstract painting and sculptures using a combination of natural and industrial materials (such as wood, water and plastic). In 1953 one of his works won the Holbein Prize and capturing the attention of Jiro Yoshihara. 1955 Yoshihara invited Motonaga to join the Gutai group which he left again in1971.
In 2011, the Guggenheim in New York commissioned him to recreate the Work (Water) for the 2013 exhibition: Gutai: Splendid Playground.