Prince Stanisław Albrecht "Stash" Radziwiłł (21 July 1914 – 27 July 1976) was a Polish nobleman and a scion of the Polish-Lithuanian princely House of Radziwiłł. His parents were Janusz Franciszek, Prince Radziwiłł (1880–1967) and Princess Anna Lubomirska (1882–1947). Stanisław had two elder brothers, Edmund Radziwiłł (1906–1971) and Ludwik Radziwiłł (1911–1928). Through his father, Stanislaw Albrecht was second cousin twice removed of Sophie, Duchess of Hohenberg, wife of the heir to the Austro-Hungarian throne Archduke Franz Ferdinand of Austria.

Radziwiłł married Countess Rose de Mauléon (1913–1996)^[2] on 10 April 1940. They had no children and their marriage was annulled in 1945. She later married Baron de Chollet, a Swiss banker.^[3]

Radziwill married Grace Maria Kolin on 2 May 1946. They were divorced in 1958. The marriage produced one son:

Grace Maria Kolin later married William Ward, 3rd Earl of Dudley (1894–1969) as his third wife,^[4] and from 1975, she lived with Robert B. Silvers.^[5]

Radziwiłł married Caroline Lee Bouvier Canfield on 19 March 1959. They had two children:

Radziwiłł was one of the organisers of the Sikorski Historical Institute in London and founder of St. Anne's Church at Fawley Court, the site of Divine Mercy College, a school for boys of Polish origin, set up by the Marian Fathers in 1953 near Henley-on-Thames, England.

He died on 27 July 1976, in London at the age of 62. His body was interred in the crypt of St Anne's Church at Fawley Court.^[6] As of 2010 the Marian Fathers were seeking authorisation to exhume the body following the closure of Divine Mercy College (in 1986) and the sale of Fawley Court (2010).

Upon becoming a British subject and in keeping with standard practice, Radziwiłł would have needed permission from Queen Elizabeth II to use his princely title,^[3] but did not receive special dispensation and was known in Britain as Mr. Radziwiłł legally and as Prince Radziwiłł by courtesy.