The unparalleled career of Michael Phelps of the USA will conclude at Rio 2016 as the most decorated Olympian competes at his fifth Olympic Games.

Splash landing: Michael Phelps takes the plunge at Rio 2016 in his first training session

Phelps, winner of 18 gold medals in swimming and 22 in total, has the chance to add three individual medals to his tally, having won the 100-metre and 200-metre butterfly and 200-metre individual medley at the US trials.

              (Photo: Getty Images/Tom Pennington)

The 31 year-old could become the first swimmer to win the gold medal in the same event in four consecutive Games (100-metre butterfly and 200-metre IM). He also is projected to compete in three relays, meaning he could take his final haul to 24 golds and 28 medals.

USA swimming superstars poised to battle for places at Rio 2016 Olympic Games

Phelps will renew rivalries with adversaries such as Chad Le Clos of South Africa and Laszlo Cseh of Hungary in the butterfly events. He will face 21-year-old all-rounder Kosuke Hagino in the medley and one final joust with his old friend and rival, 11-time medallist Ryan Lochte of USA.

              (Photo: Getty Images/Tom Pennington)

Of the 908 swimmers (492 men and 416 women) entered for the week-long action in the Olympic Aquatics Stadium, Katie Ledecky of USA, still unbeaten in an international championship, could prove the stand-out performer as she seeks a freestyle treble at 200 metres, 400 metres and 800 metres that was last achieved by Debbie Meyer of Australia in the 1968 Mexico City Games.

Australia secured a double-double in the backstroke at the world championships in 2015 as Mitch Larkin and Emily Seebohm won the men's and women's 100-metre and 200-metre respectively. There will be new champions in both races, as London 2012 winners Matt Grevers of USA and Tyler Clary of USA both failed to qualify. Larkin will face USA pair David Plummer and Ryan Murphy in the shorter race and heads the rankings in the 200-metre.

The United States team have won most medals at each of the last six Olympic Games but will be hard pressed to match the 16 golds they won in the pool at London 2012 – 50 per cent of the 32 titles on offer.