Uchimura, who won silver in the all-around four years ago in Beijing, was not at his scintillating best but scored 92.690 to see off the challenge of German Marcel Nguyen in silver medal position with American Danell Leyva in bronze, just under two points off the lead.
Britain’s Thomas finished seventh and Purvis 13th, bettering the 20th-place finish earned by both Neil Thomas at the 1992 Barcelona Games and Daniel Keatings four years ago in Beijing.
A mistake on his landing from the vault effectively cost Thomas a bronze medal because if he had produced the same score as he had in qualifying he would have come home in third, adding to the team bronze he won earlier in the week.
But his final position is still the finest by a British competitor in over 100 years. Walter Tysall was the last Briton to win a men’s all-around medal, picking up silver in 1908.
“I’m happy,” said Thomas. “If I’d landed the vault, it maybe could have been a medal but sometimes it happens, sometimes it doesn’t. All my other pieces couldn’t have gone any better.”