Caster Semenya starts a red-hot favourite to upgrade on her Olympic silver medal from London four years ago after enjoying a peerless campaign this summer.
The 2009 world champion has endured several below-par seasons since 2012, but this year the South African has so far proved invincible with eight 800m wins in as many races, including four IAAF Diamond League victories and the African title.
Semenya has also registered three of the four fastest times in the world this year, but perhaps most impressive has been the way Semenya has run most of the races with seemingly something to spare.
Her national record of 1:55.33 in Monaco last month elevated the 25-year-old to 12th on the world all-time list, while some experts believe Jarmila Kratochvilova’s 33-year-old world record of 1:53.28 could even be vulnerable in Rio.
The best of the rest this season has been Francine Niyonsaba.
The Burundian athlete, who placed sixth in the 2012 Olympic final, started the year with a bang by clinching the world indoor 800m crown in Portland.
During the outdoor campaign, Semenya has inflicted three defeats out of three on the 23-year-old, but three sub-1:57 performances also prove that Niyonsaba is a top-class athlete and she will be boosted by her national record time of 1:56.24 set in Monaco last month as she bids to be her country's first female Olympic medallist in any sport.
The 2013 world champion and 2015 world bronze medallist Eunice Sum has been a formidable championship performer in recent times. With a season’s best of 1:57.47 – also recorded in Monaco – it would be unwise to write off the Kenyan’s chances, despite the dominance of Semenya.
Look out too for her teammate, the 20-year-old Margaret Wambui, who secured victory at the Kenyan Olympic Trials and banked bronze in Portland in March.
Consistent Bishop a threat
The non-African challenge is led by Canada’s world silver medallist Melissa Bishop, who emerged last year as a world-class force.
The 27-year-old Pan American Games champion has enjoyed a consistent year and will have been lifted by a PB of 1:57.43 in Edmonton in mid-July.
World champion and 2014 European champion Mariya Arzamasova is also entered and her record alone should earn respect. The Belarusian has a relatively modest season’s best of 1:59.65 and has not competed since 10 June, but her build-up is not too dissimilar to her season ahead of last year's World Championships.
Others who have performed well this season include 2012 European champion Lynsey Sharp of Great Britain, who raced to a lifetime best of 1:57.75 in Monaco. Her compatriot, the World Championships fifth-place finisher Shelayna Oskan-Clarke, is another to watch.
Another threat could be Renelle Lamote of France, who impressed at the IAAF Diamond League meeting in Birminghamwith a PB of 1:58.01 and backed it up to the take silver medal at the European Championships last month.
The US challenge is led by world Indoor silver medallist Ajee’ Wilson and supported by US champion Kate Grace.
Recently crowned European champion Natalya Pryshchepa of Ukraine is another emerging talent who will be chasing a final spot. She is joined in Rio by teammate and 2012 European indoor champion Nataliya Lupu.
Cuba’s last medal at an Olympic women’s 800m was delivered 20 years ago in Atlanta courtesy of Ana Quirot’s silver but their bid for more glory is led by world and Olympic semi-finalist Rose Almanza. Morocco’s World Championships fourth-placer Rabab Arrafi is also entered.
Poland’s European 1500m champion Angelika Cichocka may specialise in the longer event but she is also entered in the 800m and a 1:58.97 run in Monaco marks her out as a potential danger over two laps.
Steve Landells for the IAAF