Maurice Arnold de Forest (9 January 1879 – 6 October 1968) was an early motor racing driver, aviator and Liberal politician in the United Kingdom.
Born in Paris, in the Rue Legendre (in the 17th arrondissement), Maurice Arnold de Forest was reportedly the elder of the two sons of Edward Deforest/ de Forest (1848-1882), an American circus performer, and his wife, the former Juliette Arnold (1860-1882). He had a younger brother, Raymond Deforest/ de Forest (1880-1912). The boys' parents died in 1882, while on a professional engagement in the Ottoman Empire, of typhoid.
Sent to live in an orphanage, they were adopted on 16 June 1887 by the millionaire Baroness Clara de Hirsch, née Bischoffsheim, wife of banker and philanthropist Baron Maurice de Hirsch de Gereuth, and given the surname de Forest-Bischoffsheim. The Hirschs had lost to pneumonia, earlier that year, their only surviving child, Baron Lucien de Hirsch (1856-1887). The de Forest children, however, have been identified as Hirsch's illegitimate sons by Juliette Arnold de Forest.
Von Hirsch died in Hungary at the age of 64 in 1896. His widow Clara died three years later, on 1 April 1899. Maurice inherited his adoptive father's residence, Schloss Eichhorn (now known as Veveří Castle) near Brünn in Moravia, then part of the Austrian-Hungarian Empire. Maurice inherited from the widow 25,000,000 Francs, as well as her estates in Rossitz-Eichhorn. Maurice von Hirsch had bought the estates in Rossitz (now Rosice) in 1881.
Maurice de Forest-Bischoffsheim was educated at Eton College and Christ Church, Oxford. In 1899 he was awarded the title Freiherr von Forest by Emperor Franz Joseph I of Austria. According to the Court Circular, on 6 March 1899, "The Emperor of Austria has given the title of Baron De Forest to M. Arnold [De] Forest and to his brother M. Raymond De Forest, both the adopted sons of Baroness de Hirsch de Gereuth, widow of the late Baron de Hirsch." Both men inherited millions of dollars from Baroness de Hirsch upon her death.