Athletic competition is at the heart of the Olympic Games, and there's nothing like a good head-to-head matchup to really make things interesting.

Some of the most compelling matchups of the Tokyo Games feature teams seeking to avenge previous losses, underdogs attempting to dethrone the most dominant athletes in their sports, and some of the greatest athletes to ever compete in their respective events going head-to-head for gold. Here are 10 such matchups that would make for must-watch viewing at this year's Olympics.

This story has been updated with the latest developments from Olympic Trials.

Katie Ledecky vs. Ariarne Titmus, Swimming

For years, Katie Ledecky has seemed unbeatable in distance races, but a shock defeat at the 2019 World Championships means that she now has a serious rival. Australia’s Ariarne Titmus chased down Ledecky in the final stretch of the 400m freestyle race that year to win the world title and hand Ledecky her first 400m loss at a major international event. Ledecky was ill at the time — she later pulled out of several events due to a stomach virus — and well off her usual pace, but Titmus’s time made her the second-fastest woman in history (behind Ledecky) in the 400m and solidified her as a challenger.

The rivalry heated up even further in June when Titmus set world-leading times in both the 200m and 400m free during the Australia Olympic Trials, both of which were good for No. 2 all-time in their respective events. That puts Titmus ahead of Ledecky all-time in the 200m and gives Titmus the best 400m time since Ledecky's world-record swim at the last Olympics.

In addition to the 200m and 400m, Titmus — whose coach has been known to shout Ledecky’s name during training sessions as a motivational tactic — will also compete in Ledecky's signature event, the 800m free. However Ledecky, who owns the top 24 times ever in the 800m, remains the clear favorite in that one.

Ledecky is chasing history at these Olympics. She’s expected to take part in five events (four individual races and one relay), and if she were to sweep all of them, she could potentially become the first American woman to win five gold medals at a single Olympic Games, and the first woman from any country to win 10 career gold medals.

Dates to mark: July 26 (400m final), July 28 (200m final), July 31 (800m final)

Softball has been played at four previous Olympics. The first three editions (1996, 2000, 2004) were all won by the United States, and it appeared that Team USA was again on track to win gold in 2008 after a dominant run through the round-robin prelims in which they beat each of the seven other teams by a combined score of 53-1.

But the gold medal match between the U.S. and Japan produced a surprising result. The Americans had already beaten Japan twice thus far in the tournament – once in the round robin, and then once more in the semifinal round – but this time Japan got two early runs and held on for a 3-1 victory to become Olympic champions and end Team USA’s dominant stranglehold on the sport. Then softball was dropped from the Olympic program, leaving Japan as the reigning champions for 13 years now.

The two women who pitched for the U.S. in that gold medal game, Cat Osterman and Monica Abbott, will be part of the U.S. squad headed to Tokyo. The winning pitcher from that game, Japan’s Ueno Yukiko, will be there too.

With softball not on the 2024 Olympic program, this will be the last chance (for now) for the U.S. to avenge that defeat, but they’ll have to overcome a strong Japanese team playing at their home Olympics. The two teams will meet on the last day of the preliminary round in what could potentially be a significant matchup, and it wouldn’t be a surprise to see them play again the very next day in the final as well. They've met in the final of every world championship or Olympic tournament since 2006, with the U.S. winning 7-6 in extra innings at the most recent world championships in 2018. 

Dates to mark: July 26 (preliminary match), July 27 (possible gold medal match)

The strongest of the three groups for the women’s soccer tournament is arguably Group G, which features the United States, Sweden, Australia and New Zealand. While Australia and Sam Kerr, who led the Women’s Super League in goals this season, will present a test for the United States, it’s the match against Sweden that American fans will most look forward to.

Five years ago at the Rio Games, the United States was the clear favorite for gold. The Americans were the three-time defending Olympic champions and reigning World Cup champions, but they were surprisingly eliminated by Sweden in the first round of the knockout stage after the match went to a penalty shootout. Sweden’s coach at the time, Pia Sundhage, was a former USWNT manager. Her team played a highly defensive game to slow down the U.S. attack, which ultimately helped send the game to penalties. The tactic didn’t sit well with U.S. goalkeeper Hope Solo, who famously criticized Sweden afterward for their passive gameplan.

The two teams renewed their rivalry during the group stage of the 2019 World Cup, with the USWNT exacting revenge in the form of a 2-0 scoreline. Sweden, which is FIFA’s third-highest ranked team among the Olympic entrants, has been drawn into a group with the U.S. at five straight World Cups, making this one of the most frequently played fixtures at major tournaments.

Other exciting matchups could await the USWNT in the knockout stage. In particular, a fixture against the Netherlands would be a fascinating rematch of the World Cup final, and playing Japan on their home soil would be very entertaining, especially if fans are present.

Date to mark: July 21 (group stage match)

Entering this season, the men's 400m hurdles record (46.78 seconds) set by Kevin Young at the 1992 Games was the oldest world record in men’s track. It was expected to fall at some point this year, but in a twist, it happened before any of the three contenders arrived in Tokyo.

U.S. star Rai Benjamin, who turns 24 in July, was the first to get close after running a 46.83 — just .05 seconds off the record — at Olympic Trials in June. That temporarily put him at No. 2 all-time. Temporarily, because two-time reigning world champion Karsten Warholm (25, Norway) came out a week later and finally took down the record during a Diamond League meet in front of a home crowd in Oslo.

Winning gold at the Olympics might now require breaking the new world record: Warholm's 46.70. While the Norwegian now enters Tokyo as the slight favorite, he will be challenged by both Benjamin and Abderrahman Samba (25, Qatar). Samba is the fourth-fastest man ever and the only other athlete to ever finish with a time under 47 seconds.

With the world record on the line and three of the four fastest men ever in the field, this race has become one of the most anticipated track & field events of the Tokyo Olympics.

Date to mark: Aug. 3 (men’s 400m hurdles final)

Team USA’s Ryan Crouser, his teammate Joe Kovacs, and New Zealander Tom Walsh finished 1-2-3 in men’s shot put at the last Olympics. That same trio will be expected to earn spots on the podium once again, but it remains to be seen who walks away with gold this time.

The 2019 World Championships featured arguably the greatest men’s shot put competition ever thanks to the three of them. Crouser, Kovacs and Walsh all finished within one centimeter of each other on their throws, and any one of those throws would have been a new championship record, but it was Kovacs who eked out the victory by the narrowest of margins. Together they’ve combined to win the last four major global titles: Kovacs earned world titles in 2015 and 2019, Crouser won Olympic gold in 2016, and Walsh won the world title in 2017.

For quite some time now, all three men have been chasing the world record (23.12m) set by Randy Barnes in 1990. Crouser, 28, was the one to finally topple it though, and he did so in dominant fashion with a 23.37m throw during Olympic Trials in June. That record-setting toss now sets him up as the favorite in Tokyo for what promises to be an exciting competition.

Although the U.S. has won the gold medal in men’s shot put at 18 of 28 Olympics, no American has successfully defended their title since 1956. Crouser will look to break that trend, and all three shot putters will take aim at Crouser's new world record as they try to produce another dramatic final. Currently Crouser, Kovacs and Walsh all rank within the top six all-time.

Date to mark: Aug. 5 (men’s shot put final)

April Ross has won medals in both of her previous Olympic appearances — silver in 2012 with Jen Kessy, bronze in 2016 with Kerri Walsh Jennings — but has yet to add gold to her collection. Now, headed to her third Olympics with her third different partner, she stands a strong chance of finally getting it.

Nine months after the last Olympics, Ross and Walsh Jennings announced their split, leaving both players searching for a new partner. Ross ultimately teamed up with former indoor volleyball player Alix Klineman, and together they have blossomed as a duo, earning a silver medal at the last world championships in 2019 and ascending to No. 1 in the Olympic rankings. (Walsh Jennings and current partner Brooke Sweat ultimately did not qualify for Tokyo.)

While Ross and Klineman are firmly in the gold medal discussion, another team is right there alongside them. The Canadian duo of Sarah Pavan and Melissa Humana-Paredes, who also formed a partnership after the 2016 Games, are currently No. 1 in the world rankings (which differ slightly from Olympic rankings) and were the team that beat the Americans in the final to win that last world title.

While the Canadians have the bragging rights thanks to their win at the world championships, the Americans have had the upper hand since then. Since tournaments resumed last summer, Klineman and Ross have beaten Pavan and Humana-Paredes in all four of their head-to-head meetings. If the top two seeds live up to expectations at the Olympics, another rematch could be in the cards in Tokyo.

Dates to mark: Aug. 1-6 (knockout stage)

The last Olympics produced an iconic match between Helen Maroulis and Saori Yoshida. The Tokyo Games could be remembered for Kyle Snyder vs. Abdulrashid Sadulaev.

Snyder is Team USA’s youngest-ever Olympic wrestling champion. Sadulaev, the “Russian Tank,” is considered by many to be the best pound-for-pound wrestler in the world right now. Both won freestyle gold medals at the 2016 Games — Sadulaev at 86kg, Snyder at 97kg — but then Sadulaev moved up to the 97kg weight class afterward, and a great rivalry was born.

They first faced each other at the 2017 World Championships, with Snyder pulling off a come-from-behind win over Sadulaev in the final to take the title. They met again in the final one year later, but this time Sadulaev pinned Synder in 70 seconds. A 2019 rematch never materialized — Snyder lost in the semfinals before getting to face Sadulaev, while Sadulaev rolled through the bracket to win a second straight title.

The Olympic postponement means that wrestling fans have had to wait yet another year for the rivalry to be renewed, but if this head-to-head match materializes in Tokyo, it will be must-see viewing.

Date to mark: Aug. 7 (possible men’s 97kg freestyle final)

Judo is extremely popular in Japan and has accounted for more of the country’s gold medals than any other sport. As such, it will be one of the most closely followed sports within the Olympic host nation, and one matchup that could generate the most excitement would be a heavyweight showdown between France’s Teddy Riner and Japan’s Harasawa Hisayoshi.

Riner has been judo’s most dominant athlete of the last decade. The two-time reigning Olympic champion in the men’s heavyweight (100+ kg) class amassed a 154-match winning streak from 2010-2020 that was finally ended last year by Japanese judoka Kageura Kokoro. Despite Kageura’s win, it was Harasawa, the current world No. 1, picked to represent Japan at heavyweight for the Tokyo Games.

The first time Riner and Harasawa ever faced off was the 2016 Olympic final, with the Frenchman winning the bout and earning his second gold medal. Riner was also victorious in another head-to-head bout, which came at a Grand Prix event in 2019. But two surprise defeats suffered by Riner during the 2020 season have added some intrigue to a potential Olympic rematch. Watching Harasawa take down a judo legend on home soil at the famed Nippon Budokan would be a signature moment in Japan.

Date to mark: July 30 (men’s heavyweight tournament)

New Zealand’s Lisa Carrington and Hungary’s Danuta Kozak are the two biggest names in women’s kayak racing. Carrington has dominated K-1 200m events (two straight Olympic gold medals, seven world titles), and Kozak has dominated the K-1 500m (two straight Olympic golds, three world titles) while also leading Hungary to victory in K-2 and K-4 500m events (three Olympic golds, nine world titles).

Both athletes could enhance their legacies in Tokyo by three-peating in their best individual events – Carrington in the K-1 200m, Kozak in the K-1 500m – but the K-1 500m will be particularly interesting because Carrington is expected to be Kozak’s biggest competition. Carrington, who was the K-1 500m bronze medalist at the last Olympics, beat Kozak in 2019 to become the event’s reigning world champion. Kozak finished third in that race.

If Carrington wins the K-1 200m event – she’s the heavy favorite – and then beats Kozak in the K-1 500m, she would be the first woman to sweep both of the individual kayak events since the Olympic program expanded in 2012.

This matchup could also extend to the two-person (K-2) and four-person (K-4) races. Hungary swept those two events at the last Olympics thanks in part to Kozak, but Carrington also plans to take part in both of those races this year.

Date to mark: Aug. 5 (women’s K-1 500m final)

The All Blacks of New Zealand are rugby’s most successful and most well-known team, but to win the Olympic title, they'll likely have to go through at least one of South Africa or Fiji.

New Zealand’s rivalry with the Springboks of South Africa is arguably the biggest one in the sport. The first rugby union match between the two countries was played 100 years ago, and since then, it’s earned a place in history thanks to the quality of the two teams, the intensity of the matches, and even the political significance of past meetings (some of which are documented in the 2009 film “Invictus”). And although the bulk of that history comes from rugby union (the sport’s traditional 15-a-side version), the rugby sevens teams from both countries have likewise been consistently among the best in the world.

Meanwhile another country has matched the success of those two teams in rugby sevens: Fiji. The Flying Fijians became one of the best stories of the Rio Olympics — which featured rugby on the program for the first time since 1924 — when they captured gold in the men’s tournament, knocking out New Zealand in the quarterfinals along the way. Since the inception of the annual World Rugby Sevens Series in 1999, Fiji has never finished worse than fourth in the standings, and they’ve won the title three times since the 2014-15 season.

New Zealand, South Africa and Fiji have combined to win 20 of the 21 titles awarded in the World Rugby Sevens Series, so any matchups between those three teams could help decide who wins the gold medal. The United States, led by Carlin Isles and Perry Baker, has also been riding high in recent years and has elevated itself into a medal contender. If the Eagles face off with any of those three teams during the tournament, add that to your viewing calendar as well.

Dates to mark: July 26-28 (men’s rugby tournament)