Ivanovic reached her first Grand Slam semi-final in seven years when she beat Ukraine's Elina Svitolina 6-3, 6-2 while Safarova booked a place in the French Open last four for the first time by seeing off Garbine Muguruza 7-6 (7/3), 6-3.
Serb seventh seed Ivanovic, 27, last made the semi-finals of a major on her way to her only Grand Slam title in Paris in 2008.
It will be her fifth last-four appearance at a major following similar runs to the 2007 and 2008 semi-finals at Roland Garros, Wimbledon in 2007 and the Australian Open in 2008.
"It was very tough to play today. The wind was really strong and the ball was bouncing all over the place so I just needed to stay calm and use my feet more."
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Ivanovic and Svitolina, who was bidding to become the first Ukrainian woman to reach the semi-finals of a Grand Slam, exchanged breaks in the second and third games of the opening set.
But the vastly more experienced Serb, watched from the stands by German World Cup-winning boyfriend Bastian Schweinsteiger, broke again for 3-1 to lay the foundation for clinching the first set.
Ivanovic was rewarded for her positive approach on Court Philippe Chatrier, her 37 winners to just eight for Svitolina telling its own tale.
Out on Court Suzanne Lenglen, Czech left-hander Safarova, 28, followed-up her fourth-round defeat of world number two and defending champion Maria Sharapova with a straight sets beating of 21-year-old Muguruza.