German artist Thomas Ganter has won the annual BP Portrait Award for Man With A Plaid Blanket.
Ganter's picture, for which he wins £30,000, depicts a homeless man and was praised by the judges for its "intensity".
The second prize of £10,000 went to Bath-based teacher and artist Richard Twose for his portrait of pensioner Jean Woods.
Ganter's picture will go on show at the National Portrait Gallery in London.
Ganter, who also won a National Portrait Gallery Trustees' commission worth £5,000, said he met the subject of his painting, a man called Karel, after a visit to a museum.
"After being in a museum, I saw a homeless man and was stunned by a similarity: the clothes, the pose, and other details resembled what I just saw in various paintings," he said.
"However, this time I was looking at a homeless person wrapped in a blanket and not at the painting of a saint or noble in their elaborate garment.
"By portraying a homeless man in a manner reserved for nobles or saints, I tried to emphasise that everyone deserves respect and care.
"Human dignity shouldn't be relative or dependent on socio-economic status."
Karel, who earns money by cleaning car windscreens, attended five sittings for the portrait, during which Ganter painted his head and hands, before using a life-sized doll to help him paint the clothes and the blanket.
New Yorker David Jon Kassan won the £8,000 third prize for a portrait of his mother.
Now in its 35th year, the competition received a record-breaking 2,377 entries from 71 different countries, up from 1,969 last year.
Gallery director Sandy Nairne said: "Selected from an ever-more international entry of brilliant portraits, these prize-winners represent contemporary art at its most skilled and engaging."
Ganter's painting can be seen at the National Portrait Gallery from 26 June to 21 September, along with 52 of the other entries.