German Jan Frodeno hijacked the sprint finish of former gold medallist Simon Whitfield to take the title in only the third staging of the event at the Olympics.
The inaugural champion was Whitfield in Sydney but the Canadian had to be satisfied with silver this time round after Frodeno fought back on the home stretch and overtook him with metres to go.
Frodeno finished in a time of one hour 48 minutes and 53 seconds, with Whitfield five seconds behind and New Zealand's Bevan Docherty, the silver medallist in Athens, seven seconds behind the Canadian.
The trio rounded the final bend together - with world champion Javier Gomez of Spain fading after featuring prominently with compatriot Ivan Rana - and the Canadian set off in what looked like a sprint to secure the gold.
However, Frodeno dug out a blistering finish and captured the lead as Whitfield resigned himself to silver, with Docherty a safe distance behind.
Gomez and Rana were fourth and fifth, respectively, with another German, Daniel Unger, 50 seconds of his countryman in sixth place.
There was nothing to choose between in the field after the swim and much the 40km cycle was spent together as well, until Belgian Axel Zeebroek and Luxembourg's Dirk Bockel made a break for it.
The pair made good progress and congratulated each other as they rode to the final changeover with the chasing pack out of sight. But they hadn't done enough and were sucked back into the group as the top six and Britain's 20-year-old Alistair Brownlee made the running.
The latter dropped off, however, and finished a creditable 12th, while Zeebroek was 13th and Bockel 25th.