Jennifer Saunders and Joanna Lumley will return to their roles as international PR guru Edina Monsoon and sex-crazed magazine editor Patsy Stone in the award-winning sitcom.
Original cast members Julia Sawalha, June Whitfield and Jane Horrocks will also star in the three 30 minute episodes.
Absolutely Fabulous first aired in 1992 and finished with a special episode titled 'White Box' in 2004.
The new specials will be set in the present day, where Eddy and Patsy are still working in the PR and magazine businesses.
In the first episode, fans will "rejoin the beloved ensemble in the midst of a life-changing experience for one", while the final third episode will feature Eddy and Patsy's own special influence on the London 2012 Olympics.
"It's great that we are able to celebrate our 20th birthday with all the original cast. Like a good bottle of champagne we hope that we have got better with time without losing any of our sparkle," said Saunders.
"Last week when we started filming in dear old West London, it was as if nothing had changed. It was raining. Nevertheless, we are so happy to be working for an audience that has grown just a tiny bit older like us, but is still willing to let us fall over on TV in the name of PR."
BBC Comedy executive producer Jon Plowman added: "Viewers have been fantastically loyal in their devotion to our show, so we're really thrilled to say that it's coming back for three new shows to celebrate our 20th anniversary. All of the originals who are back together again are still truly absolutely fabulous and the new adventures of Edina, Patsy, Saffy, Bubble and Mother, plus a few surprising guests, will be a real treat for viewers."
Watch Jennifer Saunders's character Edina being pulled over for drink driving below: