Kadidiatou Diani's fourth goal of the tournament, a header in the 15th minute, sparked an eight-minute three-goal Les Bleues blitz, with Kenza Dali and Le Sommer also scoring at Hindmarsh Stadium, ending the North African side's fairytale run.
France next face hosts Australia in the quarter-finals on Saturday in Brisbane.
Morocco became the lowest-ranked team (72) to play in the last 16, bouncing back from a 6-0 rout by Germany to beat South Korea and Colombia. But they were no match for fifth-ranked France who went unbeaten in the group stage, capped by a dramatic 6-3 win over Panama.
Le Sommer increased her all-time leading goalscoring record for France to 90, while the game marked the first time Les Bleues had scored four goals in a World Cup knockout game.
Diani, who netted a hat-trick against Panama, was unmarked in the box for an easy header from Sakina Karchaoui's cross that kicked off the scoring and had Moroccan keeper Khadija Er-Rmichi smacking her fists on the pitch in frustration.
There was more frustration to come. Dali connected five minutes later when she struck Diani's cross, her long shot ricocheting off the inside of the far post and in.
Le Sommer was able to get a boot on the ball for her first goal in the 23rd minute after Diani pressured a Moroccan defender.
The 34-year-old Olympique Lyonnais forward netted her second in what had been an otherwise quiet second half for France, heading in a long cross from Vicki Becho from the far post in the 70th minute.
This World Cup marked the first time three African nations made the last 16 in Morocco, South Africa and Nigeria.
Morocco were hoping to become the first African nation to win a knockout game.
Nouhaila Benzina had also made history as the first player to wear a hijab in the Women's World Cup.