A portrait of charity founder Camila Batmanghelidjh has gone on display at the National Portrait Gallery.
The portrait was painted by Dean Marsh, who won first prize in the National Portrait Gallery's BP Portrait Award, in 2005.
Marsh said he was drawn to the sitter's distinctive dress style.
Tens of thousands of youngsters living in inner-cities have benefitted from the work of Kids Company, which Ms Batmanghelidjh set up in 1996.
The charity has raised £40m since it was set up in a disused railway arch in Camberwell, south London.
Ms Batmanghelidjh said: "I hope my being on the walls of such a prestigious establishment and being painted by such a talented artist as Dean Marsh will serve to inspire children to follow their dreams no matter what the struggle.
"Every day we are enriched by our ability to love.
"However, I never thought it would lead to my fat bottom on the walls of the National Portrait Gallery!"
Marsh's work, Giulietta Coates, won him the £25,000 National Portrait Gallery's BP Portrait Award and the commission to undertake a portrait of Ms Batmanghelidjh for the gallery.
He said he found inspiration in the portraits of 19th century French artist Jean-Auguste-Dominique Ingres, when painting the Iranian-born psychotherapist and social reformer.
Marsh said: "It was a privilege to meet and paint somebody who has had such a positive effect on so many kids' lives."
The portrait joins other works in the National Portrait Gallery's Collection of commissions of BP Portrait Award-winning artists including J K Rowling by Stuart Pearson Wright, Sir Peter Mansfield by Stephen Shankland and Dame Helen Mirren by Ishbel Myerscough.