A statement from Kensington Palace confirmed that the Duke of Cambridge is leaving the military after seven-and-a-half years of service.
He completed his final shift as an RAF search and rescue pilot at RAF Valley in Anglesey on Tuesday.
William, his wife Kate Middleton and their ten-week-old son Prince George will move from their Anglesey home to Kensington Palace "within the next few weeks".
The Prince will now focus on his royal duties and his charity work, and is "currently considering a number of options for public service, a further announcement on which will follow in due course," the statement said.
He will "continue to support the work of The Queen and the Royal Family through a programme of official engagements, both at home and overseas, with The Duchess of Cambridge," and over the next 12 months, will "work closely with the Royal Foundation of The Duke and Duchess of Cambridge and Prince Harry."
The 31-year-old also plans to "expand his work in the field of conservation particularly in respect of endangered species", and will "continue to expand his charities on issues relating to children and young people, veterans and serving members of the Armed Forces."
William graduated from his search and rescue training course three years ago after being seconded to the RAF from the Household Cavalry.
As a member of C Flight of Number 22 Squadron, at RAF Valley in North Wales, flying the Sea King helicopter, the Prince took part in a number of successful operations, most notably helping to rescue Russian sailors whose ship sank in the Irish Sea.
Last month he paid tribute to locals on the island of Anglesey, where the couple lived a relatively simple life in a rented five-bedroom farmhouse, for their kindness.
They were rarely bothered by residents, who became used to seeing them going about their daily business, with Kate shopping in supermarkets and taking walks on the beach with Lupo.
In a speech, which he opened by attempting a few words in Welsh, he said: "I know that I speak for Catherine when I say I have never in my life known somewhere as beautiful and as welcoming as Anglesey. The views across the Menai straits are undoubtedly among the most stunning in the British Isles.
"I know that both of us will miss it terribly when my search and rescue tour of duty comes to an end next month and we have to move elsewhere.
"From the bottom of my heart, thank you for making my wife and me so welcome when we arrived here, as you do thousands of visitors each year.
"This island had been our first home together, and it will always be an immensely special place for us both.
"Catherine and I look forward to returning again and again over the coming years with our family."