William Reinhold Valentiner was a German-American art historian, art critic and museum administrator. He was educated and trained in Europe, first working at the Mauritshuis in The Hague and at museums in Berlin.
In 1907 he moved to the United States to become the first curator of the department of decorative arts in the Metropolitan Museum in New York City. After returning to Europe to serve in the German Army in World War I, Valentiner later was appointed to other positions in the US. From the mid-1920s, he strongly influenced the development of museum administration in the United States.
He served as director of the Detroit Institute of Art in Michigan, from 1924 to 1945. Valentiner became a naturalized US citizen about 1930 and lived in the country for nearly half his life in total. During the early 1930s, he commissioned Mexican artist Diego Rivera to create a 27-panel mural series about Detroit industry for an interior court of the museum, and gained the patronage of Edsel Ford for the project. While controversial in content, the work attracted thousands of new visitors and led to the museum being granted a larger budget by the city.