The Chinese second seed, who won the Australian Open in January, made 35 unforced errors in a 7-5 3-6 6-1 loss to world No.103 Kristina Mladenovic of France, who will next play American Alison Riske.
According to the BBC, big-serving Ivo Karlovic beat men's 11th seed Grigor Dimitrov 6-4 7-5 7-6 (7-4).
The report mentioned that it is the first time that both reigning Grand Slam champions have lost in the first round of the next major, after Swiss ace Stanislas Wawrinka's defeat on Monday.
The last Australian Open women's champion to lose in the first round at Roland Garros was American Lindsay Davenport in 2000, the report added. (ANI )