Mary Lavater-Sloman was born in Hamburg, Germany, the daughter of a wealthy shipowner, and attended private schools. She began writing as a child. In 1909, her family moved to St. Petersburg, Russia, where she met Emil Lavater, a Swiss engineer. In 1912, they were married in Zurich, and the following year had a daughter. The couple returned to live in Moscow and had a son born in 1916. They escaped the Russian Revolution to Greece, where they lived for a couple of years before going back to Switzerland. They had two more children. In 1935, she made her literary debut with The Swiss King, an historical novel, which was followed by many celebrated historical biographies, often of famous women, including Lucrezia Borgia and her Shadow (1952) and Mistress of the Seas (1956), about Queen Elizabeth I. She also wrote modern fiction. She received numerous awards, including the Medal of Arts and Sciences of the City of Hamburg in 1976. Many of her works have been repeatedly republished and translated into foreign languages.