Rachel Irene Shelley was born on 25 August 1969 in Wilfordshire, England, United Kingdom, and was brought up primarily in London. She is the youngest of four children, she has an older sister and two older brothers. Shelley spent three years in Malta as a child before attending school in Huntingdon. After graduating from the University of Sheffield with a B.A. Hons in English and Drama in 1992, she joined a local theatre company in Edinburgh and set up a community theatre company in Sheffield before moving to London to further her acting career.