The 32-year-old American, who has been struggling to get back to her best after suffering a serious autoimmune disease in 2011, was one of the main attractions at the French event whose top seed will be Italian world number seven Sara Errani.
"This event was really important to me and to continue climbing up in the rankings," Williams, 26th in the standings, said.
"Unfortunately, I've suffered a back pain which has forced me to rest and miss both the Paris event and the Fed Cup the following week."
Although Williams has pulled out, several big names will feature in Paris as the organisers handed wild cards to the 2009 French Open champion Francesca Schiavone, now 48th in the world, and 2011 Wimbledon winner Petra Kvitova.
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