Simona Halep fought back from a set and a break down to finally claim her first Grand Slam title.
Simona Halep is still waiting for a maiden Grand Slam title after three previous final defeats, while Sloane Stephens is the reigning US Open champion.
Simona Halep will have an opportunity to finally lift a Grand Slam trophy when she faces US Open champion Sloane Stephens in her third French Open final on Saturday.
Simona Halep reached her third French Open final where she will face US Open winner Sloane Stephens for the title.
Simona Halep's victory over third seed Garbine Muguruza also means she will retain the world number one ranking next week.
The 26-year-old Romanian tackles 2016 Roland Garros winner and reigning Wimbledon champion Garbine Muguruza for a place in Saturday's final.
Djokovic, the 2016 Roland Garros champion and former world number one, is seeded 20 this year after struggling to rediscover his best form after returning from a right elbow injury.
Halep, the runner-up in Paris in 2014 and 2017, slumped 0-5 down in the opening set to world number 83 Riske whose only win at the tournament came in 2014.
Elina Svitolina, the world number four, has now successfully defended three career titles, in Baku, Dubai and also Rome.
Simona Halep needed to reach at least the last eight and go further than world number two Caroline Wozniacki to retain the top-ranking going into the French Open.
Rafael Nadal's straight-set victory means he establishes a new Open era best for consecutive sets won on a single surface.
CoCo Vandeweghe will next face French sixth seed Carolina Garcia.
Simona Halep of Romania continued to lead the Women's Tennis Association rankings.
Despite the defeat, Simona Halep is assured of retaining the number one spot when the rankings are updated at the end of the tournament.
Simona Halep improved to 16-1 on the season and said her confidence is what keeps her going in tight matches.
Muguruza became the first major casualty of the event, suffering a shock 2-6, 7-5, 6-1 defeat to world number 100 Sachia Vickery.
Roger Federer remained at the number one spot with 10,060 points.
Simona Halep has reclaimed the world number one ranking from Australian Open champion Caroline Wozniacki, despite pulling out of last week's Dubai Championships due to a foot injury.