Michael Phelps hailed Katie Ledecky as "the best female swimmer that we have ever seen" as the American looks to add to her haul of five Olympic golds in Tokyo.

Ledecky won the gold medal in the 800m freestyle race at London 2012 at the age of 15 and went on to scoop four golds in the Rio Games five years ago.

The 24-year-old will be aiming to defend her titles in the 200m, 400m and 800m individual freestyle races, as well as the 4x200m freestyle relay.

A new event has also been added in for the women at this year's Games, with the 1500m freestyle up for grabs.

Given her achievements so far, Ledecky may well have Phelps' all-time Olympic record of 23 gold medals in her sights.

Phelps, who also holds the record for the most gold medals in individual events (13) and Olympic medals in individual events (16), believes Ledecky already has to be considered one of the greats.

"Katie and I have known each other for a long time," the 36-year-old said in a Panasonic Instagram live interview. "She is hands down the best female swimmer that we've ever seen.

"I always say one thing for her is just be her. As long as she's being herself and preparing for what she has to do, everything else will happen how it's supposed to.

"She's somebody that understands what to do in this setting and she's going to go out there and have some fun and we're going to see a lot of fast times."

Phelps also suggested Ledecky, and other athletes competing for the top prizes in Tokyo, must go into "autopilot" in order to keep their composure when it counts.

He added: "You've done the hard work, now it's just time to let it all show.

"Go out there, have some smiles, have some laughs and perform.

"From [Athens] 2004 on, I feel I was almost on autopilot because the preparation was done. All I had to do was just get on the blocks and race."

Olympics great Marc Spitz believes Michael Phelps' record of 23 gold medals will be broken by a future swimming sensation.

For the first time since 2000, the Games will happen without Phelps as a factor in the pool, and it will be the likes of Katie Ledecky and Caeleb Dressel who draw much of the global focus.

Phelps landed six golds at the Athens 2004 Games, then a record eight in Beijing four years later, surpassing Spitz's all-time best haul of seven in a single Olympics, which dated back to Munich in 1972.

Another four gold medals followed at London 2012, before Phelps signed off from the Olympics with five triumphs in 2016 at Rio.

"Records are made to be broken, a point in case being Michael breaking my record that took over 30 years to do. Stories will still continue to be written about athletes that will challenge those that came before them," Spitz said.

Spitz described Phelps' contribution as "overwhelming".

"I don't want to diminish the value of any one of Michael's medals, but the young swimmers are looking at that as a benchmark," Spitz said, speaking courtesy of Laureus.

"They shouldn't consider themselves a failure because they can't quite stay on a career for as long as he did. But someday, someone will break that record unless they change the sport of swimming where some of those events aren't competed in and they make the programme so it has less events.

"Michael took what I had done and concentrated on how he could make and create his own journey. That became the gold standard then.

"The reason people think maybe my seven gold medals were so great were that somebody actually challenged it and then broke that record. Michael’s record will go down in the same way and somebody else will be inspired by what he’s done."

According to Spitz, Tokyo 2020 is unlikely to see such feats achieved, but he highlighted freestyle and butterfly maestro Dressel as a swimmer capable of great things at the Aquatics Centre.

Dressel won two relay gold medals five years ago in Rio but topped the podium six times at the 2019 World Championships, including four individual wins.

Spitz also earmarked Ledecky, already a five-time Olympic champion, as another American swimmer who could enjoy a golden Games.

"From a swimming point of view, there's some outstanding names," Spitz told Stats Perform.

"Katie Ledecky comes to mind in women's swimming. She's going to go down as one of the greatest swimmers of all time. The margins of her victories are enormous, it's incredible, it's epic in some of these performances.

"She was there during the Michael Phelps era, and there's also Caeleb Dressel who is ... I don't want to say a replacement for Michael Phelps. He's his own man and rightfully so he should be.

"He's dominated the distances and the strokes he's participated in over the last number of years. There's other people from around the world that will give those two athletes certainly a run for their money.

"The point is that I think we won’t be void in the sport of swimming with names and stories to tell."

The sporting calendar provides many memorable days throughout the year but rarely do elite events overlap as often as at the Olympics.

At this year's delayed Tokyo Games, there is the prospect of seeing several of the world's top athletes all competing for gold at the same time.

August 1 looks a good bet for the standout day in 2021.

The final round of the men's golf event could see Rory McIlroy and Jon Rahm in the mix, with Andy Murray hopeful he will meanwhile be defending consecutive singles gold medals in the tennis.

This comes on the same day that Simone Biles could potentially become the most decorated Olympic gymnast of all time.

As if that were not enough, the men's 100m final is another must-watch event.

Expectations will be high heading into that second Sunday of the Games, with examples from the past three competitions living up to their billing...

AUGUST 16, BEIJING 2008

Michael Phelps and Usain Bolt would be firmly in contention to appear on the Games' own Mount Rushmore and each enjoyed one of the finest moments of their respective careers on the same day.

Phelps had spent the opening week of the Beijing Olympics pursuing Mark Spitz's 1972 record of seven golds and had six as he entered the pool again for the 100m butterfly final, almost 12 hours before Bolt's big moment.

Seventh at the turn, the United States superstar needed a remarkable recovery to triumph over a devastated Milorad Cavic by 0.01 seconds.

Phelps would pass Spitz with his eighth gold of the Games the following day, by which point he was sharing the headlines with Jamaica's own ultimate athlete.

Bolt's blistering 9.69-second final triumph in the 100m stood as a world record until the same man beat it exactly a year later. The new benchmark remains unmatched.

And that Saturday in China also saw the small matter of Roger Federer's only gold medal, claimed alongside Stan Wawrinka in the doubles final after falling to James Blake as the top seed in the singles.

AUGUST 4-5, LONDON 2012

It is actually tough to choose just one day from the 2012 Olympics, where this weekend delivered from start to finish.

On the Saturday evening, at the Aquatics Centre, swimming prepared to say goodbye to its greatest name. Phelps and the United States won the 4x100m medley, clinching his 18th gold medal in what appeared set to be his final race.

Indeed, Phelps confirmed his retirement following the Games, only to return in predictably dominant fashion in 2016.

Across the city that same night, Team GB athletes were capping a stunning run of medals that would see the day dubbed "Super Saturday". There were six home golds in all, including big wins for Jessica Ennis, Greg Rutherford and Mo Farah in quick succession.

The drama only continued the next day, too, as Murray finally sealed a Wimbledon win over Roger Federer in the tennis event, while Bolt lit up London Stadium in the 100m.

AUGUST 14, RIO 2016

Although there will be no Bolt brilliance in Tokyo, Brazil was treated to another show as he became the first three-time winner of the 100m – later doing likewise in the 200m.

The first triumph was almost overshadowed on the track, however, coming shortly after Wayde van Niekerk had broken Michael Johnson's 17-year 400m world record by 0.15 seconds.

Again, the excitement was not reserved for athletics, with Murray in action that evening to claim another gold after coming through a four-hour epic against Juan Martin del Potro.

Murray is the only player – men's or women's – to win consecutive singles golds, while Rafael Nadal's presence added a little more stardust even though he lost the bronze final to Kei Nishikori.

A stunning Sunday also saw Biles add to the reputation she takes with her to Tokyo, a third gold on the vault making her the most decorated American gymnast.

And there was history, too, for Justin Rose, as he edged past Henrik Stenson at the 18th hole of the fourth round to become the first Olympic golf champion in 112 years.