Prince William is to leave the military after more than seven years of service, Kensington Palace has announced.
The Duke of Cambridge completed his final shift as an RAF search and rescue pilot on Tuesday.
He will now focus on royal duties and charity work together with the Duchess of Cambridge, a palace spokesman said.
The Duke and Duchess of Cambridge and Prince George are expected to move from their Anglesey home to Kensington Palace within the next few weeks.
The BBC's royal correspondent, Peter Hunt, tweeted that royal officials said the next 12 months would be "transitional" for Prince William. He will not become a "full time royal" at this stage, they said.
The duke, with the Duchess of Cambridge, will continue to support the work of the Queen and the Royal Family through a programme of official engagements - both at home and overseas, the palace added.
He will work closely over the next year with the Royal Foundation of The Duke and Duchess of Cambridge and Prince Harry.
The palace spokesman said: "He will expand his work in the field of conservation, particularly in respect of endangered species."
"The duke will continue to work with his charities on issues relating to children and young people, veterans and serving members of the armed forces."