The photograph was taken by Matt Porteous in the garden at Clarence House, following the prince’s baptism at the Chapel Royal, St. James’s Palace on 9 July.
The royal family said they “hope that everyone enjoys this lovely photograph of Prince Louis as much as they do”.
The latest photo comes hours after the royal family released four official images taken by British photographer Matt Holyoak, featuring the whole family.
In one photo, Kate and William are joined by their children, along with the Duke and Duchess of Sussex, the Prince of Wales and the Duchess of Cornwall, and the Middleton family including Kate’s sister Pippa Matthews and her husband James.
Members of the royal family appear in another photo without the Middletons, a third photo features the Cambridge five and the fourth photo is an image of just Kate and Louis.