The experienced Pole is a former world No 2 and a Wimbledon runner-up but was reduced to tears after a shock??6-2 3-6 6-1 loss to her German counterpart.
It was just the third time in 34 Grand Slam appearances that Radwanska has been sent packing in the first round,
Maria Sharapova, the defending champion, also experienced a difficult afternoon in Paris despite leaving as a winner.
Her refusal to conduct the traditional post-match interview was jeered by a crowd who had come to see the reigning French Open champion.
She obliterated??Kaia Kanepi in less than an hour and a half but it didn’t appear to be an enjoyable day’s work from Sharapova.
She was struggling with illness as he defeated the world No 50 and dropped her serve once in each set so was forced to work harder than she would have liked to seal her win.
“I totally understand that everyone usually does the interviews and answers a few questions to the crowd,” she said.??”It’s absolutely normal. I’m not making any excuses but I’ve got to do what I have to do.”
Sharapova will face fellow Russian Vitalia Diatchenko next.
Victoria Azarenka marked her return to Roland Garros with a win on Monday, easing past Spain’s Maria-Teresa Torro-Flor 6-2, 6-1 in the first round.
Azarenka missed last year’s clay-court Grand Slam during a season hindered by a foot injury but she is seeded 27 this time around and her class eventually shone through against her tenacious opponent on Court One.
The Belarusian needed just one hour and 19 minutes to get the better of the 131st-ranked Torro-Flor, who started well enough but never recovered from being broken in the fifth game of the first set.
Torro-Flor saved three break points but Azarenka eventually took the game on her fourth opportunity, broke again in game seven and then took the set 6-2 on her first set point when her opponent hit a return out.
Torro-Flor then repelled two break points right at the start of the second set but again Azarenka persisted and converted the third opportunity before losing just one more game as she saw out a comfortable victory.
The two-time Australian Open champion Azarenka has also recently battled through a bout of depression that followed a split with her long-term boyfriend as well as a parting of ways from her coach.
Her low seeding has her on a third-round collision course with top seed Serena Williams but first she must get the better of either China’s Saisai Zheng or Lucie Hradecka of the Czech Republic.
Sloane Stephens advanced to the second round where she will play British No 1 Heather Watson after inflicting Venus Williams’ second first-round defeat in the past three years. At 34, Williams was the oldest female competitor this year.