Lady Louise Windsor (Louise Alice Elizabeth Mary Mountbatten-Windsor; born 8 November 2003) is the elder child and only daughter of Prince Edward, Earl of Wessex, and Sophie, Countess of Wessex. She is the youngest granddaughter of Queen Elizabeth II and Prince Philip, Duke of Edinburgh. At the time of her birth, Lady Louise was eighth in the line of succession to succeed her grandmother, but is now eleventh after the births of her brother James, and first cousins once removed Prince George and Princess Charlotte.

Lady Louise was born prematurely on 8 November 2003 (at 23:32 GMT) at Frimley Park Hospital in Surrey after her mother was rushed there by ambulance from the Wessex home at Bagshot Park, Surrey; Prince Edward was not present for the birth because it came so suddenly. Lady Louise was delivered by the Royal Surgeon and Gynaecologist Marcus Setchell via emergency Caesarean section due to placental abruption, which caused severe blood loss to both child and mother. Louise was transferred to a neo-natal unit in St George’s Hospital, Tooting, London, as a precaution. Meanwhile, her mother remained at Frimley Park until she was well enough to be discharged, on 23 November 2003. Lady Louise’s name was announced on 27 November. She was baptised in the private chapel of Windsor Castle on 24 April 2004.

Born with esotropia, Louise underwent a 30-minute operation under general anaesthetic in an attempt to correct the problem in January 2006. The operation was unsuccessful, and she had further treatment in late 2013 that corrected her vision. At age 9, she sustained a broken arm falling off a pony.

She is a member of the Guides division, and was previously a Brownie, of Girl Guides of which her grandmother is patron and her mother is president. Her mother was a Brownie (and a member of the other Girl Guide age group divisions) when she was a child. In 29 April 2011, she was one of the bridesmaids at the wedding of the Duke and Duchess of Cambridge.