The pictures, taken by Catherine earlier this month, show a rosy-cheeked and cheerful-looking Louis having fun with the grass in the grounds of Anmer Hall, Norfolk, the family's country residence.
Louis was born on April 23, 2018, becoming fifth in line to the throne behind his older siblings Prince George and Princess Charlotte, ages 5 and 3.
Few photos of the youngest prince have been made public. The Duke and Duchess posed with him outside the west London hospital where he was born and released two photos taken by Catherine the next week.
After Louis' July christening, Kensington Palace released five official photos from the occasion, some featuring Prince Harry and Meghan, Duchess of Sussex, as well as William's father, Prince Charles, and Charles' wife, Camilla.