The eight stamps show some of the best examples of Brown’s work and link in to the Capability Brown festival being held this year.
The locations shown on the stamps are Blenheim Palace, Longleat, Compton Verney, Highclere Castle, Alnwick Castle, Berrington Hall, Stowe and Croome Park.
Royal Mail is also adding a special handstamp on all mail posted in the village of Kirkharle, his birthplace, between 16 and 22 August.
Director of the Capability Brown Festival Ceryl Evans said the stamps were wonderful:
"The Capability Brown Festival is working to raise the profile and understanding of historic landscapes and what better way to bring these stunning images into people’s lives, homes and offices than on a stamp."
As well as 8,000 Post Office branches, the stamps can also be bought online, at www.royalmail.com/landscapegardens.