Maciej Słomczyński (April 10, 1922 – March 21, 1998) was a Polish translator and writer. For his detective stories he used the pen names Joe Alex and Kazimierz Kwaśniewski.
He was the son of Merian C. Cooper, an American aviator, American Air Force and Polish Air Force officer, adventurer, and the screenwriter, director and producer of the film King Kong. His mother was an Englishwoman, Marjorie Słomczyńska née Crosby (1884–1954). He adopted his last name, Słomczyński, after his stepfather, Aleksander Słomczyński, who married Marjorie after she had not agreed to leave for the United States with Cooper. However, the fatherhood of Cooper has been questioned, among others, by his family.
In 1941, he joined the Polish resistance organization Confederation of the Nation and in 1943 the Polish Home Army. In 1944 he was arrested and imprisoned in Pawiak, from which he managed to escape. Later he moved West and served in the American Gendarmerie in France.
He debuted as a poet in 1946 in the "Tydzień" magazine in Łódź. In 1947 he returned to Poland and seven years later he moved permanently to Kraków.
After the war he was persecuted and questioned as a suspected British spy. For a few months in 1953 he worked for the State Security and he fled to Gdańsk to break the contact with the agency. Later on, he persistently refused to cooperate.
He is the author of the 1957 novel "Cassiopeia", in which he presented the attitudes of the artistic circles towards communism and the reasons, which made a great part of these circles to serve the new government.