| Margot Arnold | |
| Birth Name: | Petronelle Marguerite Mary Crouch |
| Birth Date: | May 16, 1925 |
| Birth Place: | Devonport, Devon, England |
| Death Date: | September 22, 2016 (aged 91) |
| Death Place: | New York City, New York, USA |
| Occupation: | Novelist |
| Nationality: | British (until 1953), United States (1953 to 2016) |
| Period: | 1958–1990s |
| Genre: | Mystery |
| Spouse: | Philip Remington Cook, Jr. (1949-1978) |
Petronelle Marguerite Mary Cook (née Crouch, May 16, 1925 – September 22, 2016), better known by the pseudonym of Margot Arnold, was a British-born American mystery fiction novelist.
Petronelle Marguerite Mary Crouch was born on 16 May 1925 in Devonport, Devon. She received a B.A. with a Diploma in Prehistoric Archaeology and Anthropology in 1947, and an M.A. in 1950 from Oxford University.
As a mystery writer, she was best known as the creator of the Dr. Penny Spring and Sir Toby Glendower series, about an anthropologist and an archeologist based at Oxford University, England.
She was a long-time resident of Hyannis, Massachusetts. She died in New York City, New York in September 2016 at the age of 91.