He hailed from the noble family of Le Tanneux von Saint Paul, which had moved to Prussia in the 17th century.
[1] The genus Saintpaulia of the African violet was named in his honour after he discovered it in the Usambara Mountains and had sent its seeds in 1893 to Hermann Wendland, the German botanist and Chief Royal gardener at the Herrenhausen Gardens in Hanover, who gave the plant its first description, calling it the Usambara veilchen ('Usambara violet').
He was the son of the naval officer and member of the Reichstag, Ulrich von Saint Paul-Illaire (1833-1902),[4] was promoted to lieutenant in the Prussian army.
After the First World War, he addressed the American and British delegates at the Paris Peace Conference (1919–1920) asking for restitution of the German colonies, writing under the pseudonym of 'Africanus'.
From 1912, Walter von Saint Paul-Illaire became a member of the Berlin Masonic Lodge, Zum Widder.