The Serpentine hosts regular triathlon World Cup events
Hyde Park's Serpentine lake will be the centrepiece for the London 2012 triathlon after officials approved final plans for the course.
A 3,000-capacity seating area will be constructed in the park, as well as a pontoon on the lake where triathletes will swim one 1500m lap.
After the swim, the 40km cycle and 10km run will take in Constitution Hill and Buckingham Palace.
The Serpentine will also host the Games' 10km marathon swimming event.
The marathon swim will consist of six laps of 1.67km - two more than in Beijing - and, as with the triathlon, ticketless spectators will be able to watch from vantage points in the park.
In the triathlon, the swim will be followed by the cycle race which will take competitors out of the park through Queen Mother's Gate, through Wellington Arch, down Constitution Hill and on to Birdcage Walk in front of Buckingham Palace.
Athletes will then compete in the 10km run around the Serpentine for four laps before reaching the finishing line.
"Hyde Park will be a first-class backdrop for the triathlon and marathon swim as it will allow sports fans to get really close to the action as the athletes run, cycle and swim through the heart of our capital city," said Alastair Moss, chairman of Westminster Council's planning and city development committee.
Westminster had already rubber-stamped proposals for beach volleyball in Horse Guards Parade off Whitehall, where a 15,000-seat temporary arena will be constructed with stands designed to offer a clear view across the central London skyline.
Test events will be held at both venues in summer 2011, including the International Triathlon Union World Championship Series on 6-7 August.
The temporary structures for the Olympics will be installed in June 2012, two months before the Games begin while for the Olympic events Hyde Park will be surrounded by a three-metre high temporary fence.