Johnson-Thompson made a strong start in her bid for an elusive Olympic medal, taking the lead after day one of the heptathlon.
Twice a world champion, the 31-year-old finished 14th on her Olympic debut in 2012, came sixth four years later in Rio and injury prevented her from finishing in Tokyo three years ago.
In the opening discipline – the 100m hurdles – she was eighth fastest overall before going toe to toe with two-time defending Olympic champion Nafissatou Thiam in the high jump.
Johnson-Thompson and Thiam were the only two women to clear 1.92m, and while the Belgian won the event as she needed fewer attempts to reach that height it was enough to put the Briton top of the standings after the first two events.
And she was top at the end of the day, too, after posting a new shot put personal best of 14.44m, before going on to win her 200m race in 23.45 seconds.
Those results put Johnson-Thompson on 4,055 points, 48 ahead of Thiam in second, while Anna Hall of USA sat third on 3,956, with GB’s Jade O’Dowda in 17th.
The athletes compete in long jump and javelin on Friday morning, before the 800m decides the medals.
