The stamp features an image of the royal couple leaving St Mary’s Hospital Paddington with their newly born son George Alexander Louis.
The prince was born on July 22 at 4.24pm BST with royal gun salutes across London to herald the new arrival.
The Weekender and Australia Post have five prize packs to give away, containing one commemorative cover, one stamp pack and one maxicard. Send your name, address and daytime phone number to Royal Baby Stamp Giveaway, PO Box 885, Joondalup WA 6919. Or email firstname.lastname@example.org.