Francine Niyonsaba of Burundi, world indoor champion and Olympic silver medallist, won the third and final semi ahead of Kenya's Margaret Wambui, bronze medallist at both the world indoors and Olympics previous year.
Cape Town - South Africa's Caster Semenya had her fans in raptures when she won gold in the women's 800m final at the IAAF World Championship in London after a British journalist had goaded her over her gender ahead of the race.
Sunday's victory crowns a sensational championships for the Rio Olympic champion, although it wasn't plain sailing in the 800m final.
First Wilson and then Niyonsaba took the fight to the South African, going out quickly on the first lap as Semenya settled into her usual position in the middle of the pack. The Burundian increased the pace over the next 200m, and she was followed by Wilson as they tried to leave Semenya behind in their wake.
Ajee Wilson, who set a US record of 1:55.61 last month and has been in hot form, looked superb in winning the first heat in 1:59.21 from Melissa Bishop, the 2015 silver medallist from Canada who looked more like her normal self after labouring through the first round.
The versatile athlete had also bagged the 1 500m bronze medal in the English capital earlier in the week.