With one event remaining, Belgium's Nafissatou Thiam is within range of a second consecutive Olympic gold medal in the heptathlon.
A clean two laps around the track in the 800m will make her the first heptathlete to repeat at the Games since Jackie Joyner-Kersee in 1992.
Thiam's lead is 64 points over Anouk Vetter of the Netherlands, who appears to have silver all but secured.
American Kendall Williams and Dutch athlete Emma Oosterwegel are locked in a heated battle for bronze, with only one point in it. The first to the line in the 800 may claim it, though Belgian Noor Vidts is in the mix for a medal as well.
Watch coverage LIVE on NBC starting at 5:25 a.m. ET, or stream here.
Event #7 - 800m
Begins 8:20 a.m. (ET)
Event #6 - Javelin Throw
Nafi Thiam won her second consecutive event to regain the overall heptathlon lead over Anouk Vetter.
Thiam's second of three throws was best in the entire field at 54.68m (179 ft, 4.8 in), worth 951 points.
Vetter's mark of 51.20m was fourth-best, but a full 68 points behind Thiam.
American Kendell Williams logged the seventh-best throw to lift her into a one-point lead in the bronze medal position. She'll have to beat out Emma Oosterwegel in the 800m to hang onto it, though.
TOP 5 AFTER JAVELIN (6/7)
Nafissatou Thiam (BEL) - 5912
Anouk Vetter (NED) - 5848
Kendell Williams (USA) - 5642
Emma Oosterwegel (NED) - 5641
Noor Vidts (BEL) - 5592
Event #5 - Long Jump
Belgium's Nafi Thiam, the defending Olympic gold medalist, began her charge back towards overall lead with a top mark in the long jump at 6.60m (21 ft, 7.8 in).
However, Dutch heptathlete Anouk Vetter was only 13 centimeters behind, keeping the lead but by the slimmest of margins.
The two athletes are separated by four points.
Behind them, Thiam's teammate Noor Vidts remains in bronze medal position with two Americans — Annie Kunz and Kendell Williams — close behind. Williams and Kunz managed the second- and fifth-best jumps of the event, respectively.
TOP 5 AFTER LONG JUMP (5/7)
Anouk Vetter (NED) - 4965
Nafissatou Thiam (BEL) - 4961
Noor Vidts (BEL) - 4890
Annie Kunz (USA) - 4819
Kendell Williams (USA) - 4806
Event #4 - 200m
The heptathlon gold medal will not return to Great Britain in 2021 as Katarina Thompson-Johnson suffered a re-injury to her right leg during the first heat of the 200m event.
In a moment of spirit and toughness, she refused help off the track and instead finished the race, though withdrew from the competition shortly thereafter.
It wasn't the only shakeup to the top five. Belgium's Nafissatou Thiam, who had led after the prior two events, was knocked down to the third overall spot after a disappointing 18th-place finish in the 200m at 24.90.
Anouk Vetter of the Netherlands finished third in 23.81 and emerged as the new overall leader of the competition.
TOP 5 AFTER 200m (4/7)
Anouk Vetter (NED) - 3968
Noor Vidts (BEL) - 3941
Nafissatou Thiam (BEL) - 3921
Annie Kunz (USA) - 3870
Odile Ahouanwanou (BEN) - 3867
Event #3 - Shot Put
American Annie Kunz vaulted herself into the top five with a strong throw of 15.15m in the shot put, good enough for the third-best mark at 871 points.
The leader, Belgium's Nafissatou Thiam, managed 14.82m on her first throw for the fourth-best result, more than enough to keep her lead.
The other Americans, Erica Bougard and Kendall Williams, struggled in this event, finishing 19th and 22nd, respectively. Both fell out of the top five overall.
Katarina Johnson-Thompson only managed 15th-best in the event.
TOP 5 AFTER SHOT PUT (3/7)
Nafissatou Thiam (BEL) - 3025
Anouk Vetter (NED) - 2969
Noor Vidts (BEL) - 2931
Annie Kunz (USA) - 2901
Katarina Johnson-Thompson (GBR) - 2886
Event #2 - High Jump
Defending Olympic gold medalist Nafissatou Thiam surged into the heptathlon lead with an unmatched high jump mark of 1.92m (6 ft, 3.6 in), good enough 78 points more than any other athlete in the event.
She did not even attempt a jump until 1.80m, after several of the 23 competitors had already been eliminated. Her only misses came when trying to elevate the mark to 1.95m.
American Erica Bougard and Great Britain's defending world champion Katarina Johnson-Thompson both notched the next-best result at 1.86m (6 ft, 1.2 in).
The leader after the 100m hurdles, American Kendell Williams, finished in an eight-way tie for eighth place in the high jump with a mark of 1.80m, dropping her to the fifth position overall.
TOP 5 AFTER HIGH JUMP (2/7)
Nafissatou Thiam (BEL) - 2176
Erica Bougard (USA) - 2157
Katarina Johnson-Thompson (GBR) - 2138
Noor Vidts (BEL) - 2115
Kendell Williams (USA) - 2107
Event #1 - 100m Hurdles
American Kendell Williams went out to an early lead in the event with the top time in the 100m hurdles of 12.97 out of Heat 3, which produced the four fastest times overall.
The opening event is one of Williams' strongest, and also one of the weakest for defending Olympic gold medalist Nafissatou Thiam of Belgium, who relies primarily on her jumping and throwing ability to post big scores.
Thiam finished with the 15th-best time in the event at 13.54. Great Britain's defending world champion, Katarina Johnson-Thompson, secured a solid seventh place start in 13.27.
TOP 5 AFTER 100m HURDLES (1/7)
Kendell Williams (USA) - 1129
Marthe Koala (BUR) - 1114
Anouk Vetter (NED) - 1111
Erica Bougard (USA) - 1103
Noor Vidts (BEL) - 1099