The couple will be joined by reigning monarch Queen Elizabeth Ii, Prince Charles and Prince Harry as the third in line for the throne is baptised at a chapel in St James's Palace in London on Wednesday (23Oct13).
Princess Anne's pregnant daughter Zara will act as godmother, alongside Catherine's school pal Emelia Jardine-Paterson and Julia Samuel, a close friend of the prince's late mother Diana, Princess of Wales.
Godfather duties fall to William and Harry's former private secretary Jamie Lowther-Pinkerton, the prince's childhood friends William van Cutsem and Earl Grosvenor, and Oliver Baker, who attended St. Andrews university in Scotland with the royal couple.
Their decision to choose close friends as their firstborn's godparents breaks with royal tradition of asking members of foreign royal families and the aristocracy to take on the roles.
The Duke of Edinburgh, Camilla, Duchess of Cornwall, and Catherine's parents, Carole and Michael Middleton, as well as her siblings, Pippa and James, are all expected to be in attendance at the ceremony.
The party will celebrate the baptism with a reception at royal residence Clarence House, where guests will be served cake from the couple's wedding in 2011.