William Marias Malisoff, also William Marias Malisov (1895 – 16 November 1948), was born in Russia, immigrated to the United States as a child, and became a naturalized United States citizen. Malisoff obtained a PhD. from Columbia University. He owned and operated United Laboratories, a company principally engaged in research on lubricating processes for war industries and biochemistry.
Malisoff fell under FBI scrutiny in 1940 on the basis of observed contact with KGB Officer Gaik Ovakimian. According to Venona project information, the Soviets, in 1944, were having considerable trouble with Malisoff as he wanted a sizable lump sum payment to help him establish a laboratory. When his request was flatly refused, Malisoff complained with considerable irritation "that the materials handed over by him on one question alone—oil, by his estimate had yielded the [Soviet] Union millions during past years and the aid requested by him was trifling." Malisoff was an extremely active and important agent; his Case Officer, Leonid Kvasnikov, who specialized in scientific-technical espionage, had met with Malisoff twenty times in 1943 alone. Malisoff had previously raised the funding question with Mikhail Shalyapin and Gaik Ovakimian who had preceded Kvasnikov.
In August 1943 Pavel Mikhailov, the New York Soviet Military Intelligence (GRU) Rezident sent an inquiry to Moscow regarding Malisoff. But the GRU "was forbidden to meet Malisov [Malisoff] since the latter is connected with the Neighbors [KGB]."
In 1945 Malisoff was connected with the Institute for the Unity of Science for a short time.
William Marias Malisoff, whose cover name assigned by Soviet intelligence and deciphered by Arlington Hall cryptographers were HENRY and TALENT. Malisoff is identified in the following intercepted Venona project decrpytions:
195. Venona 1276 GRU New York to Moscow, 1943; 193 KGB New York to Moscow, 8 February 1944; 620 KGB New York to Moscow, 4 May 1944; 622 KGB New York to Moscow, 4 May 1944; 1077 KGB New York to Moscow, 29 July 1944; 1403 KGB New York to Moscow, 5 October 1944; 1680 KGB New York to Moscow, 30 November 1944; 1706 KGB New York to Moscow, 4 December 1944; 1755 KGB New York to Moscow, 14 December 1944.
Writing by Malisoff
- A Calendar of Doubts and Faiths
- Philosophy of Science, editor. 
- Meet the Sciences
- The Span of Life
- FBI Venona file, pgs. 33 (PDF).
- FBI Synopsis on "Operations of the MGB Residency at New York, 1944-45"
- John Earl Haynes and Harvey Klehr, Venona: Decoding Soviet Espionage in America (New Haven: Yale University Press, 1999), pgs. 291, 325.
- Contemporary Review of Malisoff's The Span of Life, (1937).