Jamaican sprinter Veronica Campbell-Brown will attempt an unprecedented Olympic treble on Wednesday as controversial South African 800m runner Caster Semenya makes her long-awaited Games debut.
Campbell-Brown, winner of the 200m at the 2004 and 2008 Olympics, will become the first woman in history to win an individual athletics crown in three consecutive Games if she successfully defends her title once more.
The 30-year-old cruised into Wednesday's final with an impressive 22.32sec in her semi-final and declared herself ready to see off the threat of rivals who include Shelly-Ann Fraser-Pryce, Allyson Felix and Sanya Richards-Ross.
"I am happy. I have a lot of experience, I know what to expect. Tomorrow night we know that it will be an extremely difficult event," Fraser-Pryce said.
"My objective is just to stay focused - and run my heart out."
Campbell-Brown's opponents look more than capable of ending her eight-year reign as Olympic champion, however, and few would begrudge Felix in particular if the 26-year-old American strikes it lucky at the third time of asking.
Felix has finished as silver-medallist behind Campbell-Brown at the past two Olympics, but looked superb in reaching the final on Tuesday, coasting home in 22.31sec to win her semi-final.
"It has been a long time coming. I feel I am ready to put a race together," said Felix, who ran a personal best and world-leading time of 21.69sec at the US Olympic trials, the fastest for 14 years.
"I think if I put a good race together I'll run a fast time."
The battle for the 200m crown is one of 16 gold medals at stake on Day 12 of the Games on Wednesday.
In addition to the 200m, women athletes will be vying for the long jump and 400m hurdles titles while men's competition sees the 110m hurdles.
Jamaican sprint king Usain Bolt will be expected to stay on course for a repeat sprint double by booking his place in the final of the 200m following Sunday's electrifying victory in the 100m final.
The fastest man on the planet looked imperious in his opening heat on Tuesday, coasting through to the next round in 20.39sec despite virtually jogging across the line.
Meanwhile, Semenya will aim to leave the gender controversy which threatened her athletics career further in the past when she begins her first Olympics campaign in the opening round of the 800m.
The 21-year-old had to undergo drug tests followed by gender tests following her 2009 World Championships victory in Berlin and was later barred from competing for nearly a year before being cleared to run again.
Away from the athletics arena on Wednesday, China will be favoured to add to their gold tally by completing a second consecutive clean sweep of the table tennis when the men's team final takes place.
The star-studded USA basketball team will look to secure their passage to the semi-finals with victory over Australia in the quarter-finals.