Horst, born Horst Paul Albert Bohrmann, who chose to be known as Horst P. Horst when he became a US citizen, was a German-American fashion photographer working in New York. Horst studied at Hamburg Kunstgewerbeschule in the 1920's but left Germany in 1930 to study in Paris under the architect Le Corbusier. In 1930 he met Vogue photographer Baron George Hoyningen-Huene, and became his assistant, occasional model and lover. In 1931, Horst began his association with Vogue, publishing his first photograph in the French edition of Vogue that year.
Horst rented an apartment in New York in 1937, and while residing there met Coco Chanel. He would photograph her fashions for the next thirty years. He met Valentine Lawford, British diplomat in 1938 and they would live together as a couple until Lawford's death in 1991. They adopted and raised a son, Richard J. Horst, together.
In 1943, he received his United States citizenship as Horst P. Horst. He became an Army photographer.
Horst photographed many celebreties and politicians of the day including Bette Davis, Harry Truman, Noel Coward, the First Lady and Marlene Dietrich.
He continued to work for Vogue throughout the rest of his career and began photographing for House and Garden in the mid-1970s.