Robert Diez (20 April 1844 in Pößneck – 7 October 1922 in Loschwitz) was a German sculptor.
His artistic inclinations began to emerge at his grandparents home in Sonneberg, the center of the German toy-making industry.
During his years at the Gymnasium in Meiningen, he lived with his uncle Samuel Friedrich Diez, the Court Painter, who strongly encouraged Robert to pursue a career in art.
After his father died and he lost his means of support, he went to work in Schilling's studio.
He succeeded Ernst Julius Hähnel at the Master Studio for Plastic Arts and became a member of the Academic Council in 1891.