Autumn Patrica Kelly Phillips was born 3 May 1978 in Montreal, Quebec, Canada, the only daughter of Brian Kelly and his wife Kathleen, who is known as Kitty. She has one older brother, Kevin, and a twin, Christopher, they were primarily raised in Cedar Park, Pointe-Claire, Canada, which is in the English-Speaking west island region of Montreal. She was baptized on 18 June 1978, at St. John Fisher Parish Church.
Her parents divorced when she was eight years old. After the divorce, she continued to live in Cedar Park, Pointe-Claire, Canada. Her mother remarried shortly after the divorce was finalized to commercial pilot Ron Magas.
She attended private Roman Catholic schools, including St. Thomas High School, where she excelled in sports and graduated in 1999. She also attended McGill University, earning a degree in East Asian Studies in 2002. While at university, she worked various jobs including as a model and bartender.
She attended the 2003 Candaian Grand Prix, where she would meet her soon to be husband, Peter Phillips. At the time, he was working for WilliamsF1. At the time, she did not realize who exactly she had chosen to date. Six weeks after their courtship started, she realized who exactly her boyfriend was after seeing him appear on TV in the UK. The next time they saw each other, Peter had some explaining to do! Shortly after their courtship began, since she accepted a job in England anyway, she moved to England, to a Kensington flat with him, as well as frequenting Peter's cottage on his mother's estate. From there, she attended royal events (such as his grandmother's 80th birthday in 2006) while working as an assistant to Sir Michael Parkinson. During their courtship, she converted from Catholism to the Church of England, and their engagement was announced on 28 July 2007, and the queen gave her official consent on 9 April 2008, and they were married on 17 May 2008. Today, they have two daughters, Savannah Anne Kathleen Phillips (2010) and Isla Elizabeth Phillips (2012).