Team USA stormed to victory at the Rio 2016 with a stunning 121 MEDALS as they finished top of the Olympic medal table - but who are the athletes returning to defend their gold in Tokyo?

• The Tokyo Olympics is finally here after its 12-month delay due to Covid-19
• The first of the 339 events in total got underway on Wednesday morning 
• It was Team USA who stormed to victory in Rio in 2016, claiming 46 gold medals  
• But who are the athletes returning five years later to defend their crowns? 

After a five-year wait following their record-breaking victory at the Rio Games, Team USA return to the Olympics with high hopes of another dominant display. 

Their wait was extended by 12 months, with the outbreak of the coronavirus pandemic enforcing a year-long postponement. 

Regardless, Team USA return as champions, having claimed 121 medals in Rio, becoming only the seventh team in history - and the first since 1948 - to top the medal chart in every category. 

Their total was also the highest-ever achieved by a Team USA side in a non-boycotted Games, 11 more than their previous record total of 110 from the Beijing Games in 2008.   

With a number of athletes retiring since Rio, while others are either injured or failed to qualify for Tokyo, many of Team USA's gold medal stars won't return to defend their hard-earned titles this summer. 

There are still an abundance of athletes that will be competing for successive titles, however, and Sportsmail details them all below.   

Athletics    

Dalilah Muhammad (400m hurdles)

Dalilah Muhammad claimed the gold in the 400m hurdles five years ago in Rio, with a time of 53.13 seconds. 

The American's team-mate Ashley Spencer also finished on the podium, running a personal-best 53.72 seconds to claim the bronze medal.  

Muhammad will face significant competition from team-mate Sydney McLaughlin, who broke her world record when the two raced at the Olympic Trials in June. 

Matthew Centrowitz (1,500m)

Matthew Centrowitz became the first American to win a gold medal in the 1,500m since 1908 when he claimed victory at the Rio Games. 

He was also inducted into the University of Oregon Athletics Hall of Fame earlier in 2021. 

Finishing with a time of 3:50.00, Centrowitz was in utter disbelief when he crossed the line to claim the gold, afterwards saying: 'I literally was still looking at the board, like, did somebody go by me? Did I really just win?' 

Men's 4x400m

In what was the final track event of Rio 2016, Team USA claimed gold in the men's 4x400m relay race. 

A team of LaShawn Merritt, Gil Roberts, Tony McQuay and Arman Hall completed the race in two minutes 57.30 seconds, ahead of Jamaica in second. 

Randolph Ross, Michael Norman, Michael Cherry, Trevor Stewart and Vernon Norwood are included in the pool this year.  

Ryan Crouser (shot put) 

Ryan Crouser made history in Rio, as he beat Ulf Timmermann's record - set in 1988 - with a monstrous throw of 22.52m to win the gold medal. 

And to say he's coming into Tokyo in form would be an understatement. 

At the Olympics qualifier last month, Crouser broke the 31-year standing world record with a throw of 23.37 meters. He's going to take some beating this summer. 

Women's 4x100m

Team USA claimed the women's 4x100m gold medal at the Rio Olympics with what was the second-fastest time in history at 41.01 seconds. 

It was a team of English Gardner, Allyson Felix, Tianna Bartoletta and Tori Bowie who sealed the victory, having nearly crashed out in the heats. 

There, they dropped the baton and would have been out if not for a successful appeal, which saw them subsequently run on their own in the Olympic Stadium after arguing they were obstructed. 

English Gardner, Aleia Hobbs and Gabby Thomas will compete this year, alongside others who are already selected for individual events.   

Women's 4x400m

Team USA also claimed the women's 4x400m gold medal at the Rio Olympics, in what was their sixth straight Olympic title. 

A team of Allyson Felix, Phyllis Francis, Natasha Hastings and Courtney Okolo took the victory. 

Kendall Ellis, Lynna Irby and Kaylin Whitney will compete this year, alongside others who are already selected for individual events.  

Basketball

Men's Basketball

Kevin Durant led Team USA to their third successive basketball Olympic gold at the Rio Games. 

Though certainly not at their best throughout the competition, they found enough form to emphatically beat Serbia 96-66 in the final. 

Team USA will be without former head coach Mike Krzyzewski this summer, however, having taken charge for each of their victories at the 2008, 2012 and 2016 Games. 

Instead, Gregg Popovich, head coach of the San Antonio Spurs, takes charge.

Women's Basketball 

Similarly to the men's team, Team USA's women's basketball team also head into the Tokyo Games as champions and as heavy favourites to claim another gold. 

They cruised to gold in Rio five years ago, beating Spain 101-72 to win their sixth straight Olympic title. 

Team USA have been in poor form with back-to-back losses in the build-up to the Games, however, though they looked back to their best with a 93-62 win over Nigeria in their final tune-up before the start of the competition. 

Cycling 

Connor Fields (BMX) 

Connor Fields became the first American to win the BMX event since its introduction to the Games in 2008 as he took the gold in Rio. 

The American fell to his knees in celebration, after defeating the Netherlands' Jelle van Gorkom by 0.684 seconds. 

Fields now returns with a wealth of experience aged 28, as opposed to 23 when he won the gold in Rio, which he believes will only make him better this time round.  

Gymnastics 

Simone Biles (All-Around, vault, floor exercise, team)

Simona Biles is nothing other than a sensation. The 24-year-old already has four Olympic gold medals to her name, all won at the Rio Games. 

She now has her eyes set on breaking a number of records, some of which she narrowly missed out on in Rio five years ago. She will become the first woman since 1968 to win back-to-back Olympic all-around titles with victory in Tokyo.

Few would bet against her creating more history this summer, having looked impeccable when she competed in Indianapolis in May.   

Women's Gymnastics Team  

Biles will once again be competing in the Women's Gymnastics Team event, having won the gold medal last time out. 

She was joined in Rio by Gabby Douglas, Laurie Hernandez, Madison Kocian and Aly Raisman as they claimed the USA's second successive team gold. 

This time, Biles will be joined by Jordan Chiles, Sunisa Lee and Grace McCallum as they go for a third straight title.  

Rowing 

Women's Eight 

Team USA won their third-straight Olympic gold in the women's eight last time out in Rio, becoming just the second team in history - after Romania - to win the title in three consecutive Games. 

It was Amanda Elmore, Tessa Gobbo, Eleanor Logan, Meghan Musnicki, Amanda Polk, Emily Regan, Lauren Schmetterling, Kerry Simmonds and Katelin Snyder who led the team to glory last time out. 

Katelin Guregian - previously Katelin Snyder before marrying Nareg Guregian - and Meghan Musnicki are the only returning athletes this year. 

They'll be joined by seven athletes competing in their first Games.  

Swimming  

Katie Ledecky (200m, 400m and 800m freestyle) 

Katie Ledecky won four gold medals and a silver throughout a prolific Olympic Games in Rio back in 2016. 

Coming off a strong display in the US trials, Ledecky is once again the favourite to rack up a number of golds. 

She will compete in four individual events, being the 200m, 400m, 800m and 1500m freestyle.  

Lilly King (100m breaststroke) 

Lilly King returns to the Olympics as the favourite to back up her historic win in the 100m breaststroke event in Rio 2016. 

King saw off the competition from Yulia Efimova, who was controversially permitted to compete after appealing against a doping suspension.

The American also took aim at her team-mate after the victory, stating she didn't think Justin Gatlin - who had also failed a drug test previously - should be on the team.    

Men's 4x100m freestyle

Michael Phelps, Nathan Adrian, Ryan Held and Caeleb Dressel won the men's 4x100m freestyle for Team USA in Rio five years ago. 

They finished with a time of 3:09.92 to take the gold ahead of France in second and Australia in third.  

Of course, Phelps won't be there this year, though Team USA remain the favourites to prevail.  

Men's 4x200m freestyle

Again Phelps was involved as Team USA won their fourth-straight gold medal in the men's 4x200m freestyle. 

He was joined by Conor Dwyer, Townley Haas and Ryan Lochte as they clocked a time of 7:00.66 to finish ahead of Team GB and Japan. 

They'll be confident of securing another gold this year.  

Men's 4x100m medley

In what was Michael Phelps' final-ever race, Team USA took victory in the men's 4x100 freestyle event back in 2016. 

Phelps was joined by Nathan Adrian, Ryan Murphy and Cody Miller, as they clocked in with a time of 3:27:35, an Olympic record.   

Ryan Murphy (100m and 200m backstroke) 

Ryan Murphy won three gold medals at the 2016 Olympic Games, being the 100 and 200m backstroke events individually and the 4x100m medley relay. 

Murphy will return to the Games in Tokyo looking to defend both of his individual titles. 

The American put in an impressive performance at the US Olympic trials and will be confident of another gold.   

Women's 4x200m freestyle 

Katie Ledecky starred for Team USA as they won the women's 4x200m freestyle five years ago. 

She was joined by Allison Schmitt, Leah Smith and Maya DiRado as they clocked a time of 7:43.03 to see off the competition from Australia and Canada. 

Women's 4x100m medley 

Lilly King and her team of Simone Manuel, Kathleen Baker and Dana Vollmer claimed the gold medal in the women's 4x100m medley in 2016.  

They clocked in with a time of 3:53.13 to beat Australia in second and Denmark in third. 

Remarkably, it was Team USA's 1000th gold medal in the history of the summer Olympic Games.  

Tennis 

Bethanie Mattek-Sands (mixed doubles)

Bethanie Mattek-Sands and her partner Jack Sock won gold in the mixed doubles at Rio 2016, in what was the former's first participation at any Games. 

Mattek-Sands returns once again in Tokyo looking to claim another medal, after stating her achievement last time out was the best of her career. 

It's not yet confirmed whether she will compete in the mixed doubles, however, with the draw for the 16-team event announced on July 27, comprising of those already participating in singles or doubles.   

Water Polo 

Women's Water Polo 

USA's women's water polo side were another to make history in Rio by becoming the first team to ever win back-to-back Olympic titles. 

They beat Italy 12-5 in a one-sided final, with eight different scorers handing the champions a successive title. 

The US also won their seventh consecutive FINA Women's Water Polo World League title in June and come into Tokyo expected to prevail once more. 

Wrestling 

Kyle Snyder (97 kg freestyle)

Kyle Snyder claimed an historic victory at the 2016 Olympics - his first appearance at a Games - aged just 20-years-old. He was the youngest US wrester to ever win Olympic gold. 

Snyder beat Azerbaijan's Khetag Gazyumov in the final, having become the youngest world wrestling champion ever at 19 the year prior. 

Snyder believes he is coming in a more 'mature' wrestler this time round, with less stress and anxiety before competition.  

Helen Maroulis (53 kg freestyle) 

In yet another historic moment for American sport, Helen Maroulis became the first female Team USA athlete to win gold at the Olympics in 2016. 

She did it in style, beating three-time Olympic gold medalist and thirteen-time world champion Saori Yoshida in the final.  

Maroulis contemplated retiring after a pair of concussions suffered in 2018, but opted against it and returns to defend her crown.