Judy Fryd, the founder of learning disability charity Mencap, appears on a new first class stamp issued today.
Fryd, who died in 2000 and would have been 100 this year, is one of 10 people commemorated in the Royal Mail's Eminent Britons collection.
Other famous names honoured to mark anniversaries in 2009 include former Manchester United manager Sir Matt Busby (born in 1909), Sherlock Holmes creator Sir Arthur Conan Doyle (born in 1859) and former Liberal Prime Minister William Gladstone (born in 1809).
The mother of a child with a learning disability, Fryd formed the National Association of Parents of Backward Children, now known as Mencap, in 1946.
Her campaigning secured the right for every child with a learning disability to receive an education.
Mark Goldring, Mencap's chief executive, said: "The Judy Fryd stamp is a great tribute to an outstanding individual who changed the attitudes of society towards people with learning disabilities forever. Thanks to Judy's devotion to campaigning, people with learning disabilities now have a voice in society."