Knight was born to Michel Aertsens and his wife Begum Sabiha Rumani Malik (of a Pakistani Muslim family). The marriage ended in divorce shortly after India's birth. In 1975 her mother married Andrew Knight. They were divorced in 1991, after having two more daughters; Amaryllis Knight and Afsaneh Knight. India Knight began to use her first stepfather's surname at the age of thirteen. India's mother subsequently married the architect Norman Foster, Baron Foster of Thames Bank in 1994; they remained married until 1998.

Knight, a native French speaker, lived in Brussels until about the time she turned nine. After migrating to the United Kingdom, she was educated at the Lycée Charles de Gaulle school in London and at Wycombe Abbey School, Buckinghamshire. She was awarded an exhibition to Trinity College, Cambridge, where she read Modern Languages from 1984-1987, before starting her career in journalism.

In addition to writing for and contributing to major British magazines and newspapers, India Knight writes a prominent weekly column for The Sunday Times. She is also a regular guest on British radio and television. After writing an article in The Sunday Times about her daughter's special needs - her youngest child has DiGeorge syndrome - Knight launched a blog about children with special needs "for parents in a similar position to keep in touch, compare notes and help each other". The blog is called Isn't She Talking Yet?.

Knight lives in London with her three children. She remains married to, though separated from, Jeremy Langmead, with whom she has two sons. Langmead is the former editor of Wallpaper* magazine and currently the editor of Esquire magazine. Her third child's father is author Andrew O'Hagan.

Fiction

• My Life on a Plate (2000)
• Don't You Want Me? (2002)

Non-fiction

• The Shops (2003)
• The Dirty Bits For Girls (editor, 2006)
• Neris and India's Idiot-Proof Diet (2007)
• Neris and India's Idiot-Proof Diet Cookbook (2008)
• The Thrift Book: Live Well and Spend Less (2008)

Children's books

• The Baby (2007)