The stamps will feature photographs taken by Mario Testino to mark the couple's engagement and will be available at post office branches from April 21, eight days before the ceremony.
"We are honoured to be celebrating this very special and historic occasion," said Stephen Agar of the Royal Mail.
"We believe that that this set of stamps will be very popular with people both in the UK and around the world."
The postal service said the Queen gave the final approval for the issue of the stamps.
It is the third time Prince William has appeared on a Royal Mail stamp - he was featured on a sheet of stamps to celebrate the Queen and the Queen Mother's 100th birthday in 2000 and in 2003 became the first member of the royal family to have a set of stamps produced to celebrate their 21st birthday.
He is also the first of the Queen's grandchildren to have their wedding commemorated on a set of stamps.
The commemorative stamp sheet consists of two first class stamps and two 1.10 pound stamps, which capture the couple in both formal and informal poses.
The formal image was taken in the Council Chamber of St James's Palace in London while the informal image shows the couple in the Palace's Cornwall room.