The 39-year-old Williams was bidding to win a record-breaking 24th Roland Garros Grand Slam title after reaching the US Open semifinals earlier this month.
She said the injury she suffered in New York had not recovered enough to compete in Paris.
“I managed to make it a little better, but only by watching this tournament for a long time -” will I be able to go through enough matches? “And that’s why I don’t think I could and I’m trying to walk, so it’s a telltale sign that I should try to recover,” she told reporters on Wednesday.
“Definitely in the second set (from the first round match) I felt I had to limp and that was not good,” said Williams, who won three titles in Paris.
“I had to focus on walking straight so I wouldn’t limp. I tried – I always give 100% and everyone knows that – maybe even more than 100% if that’s possible.
“I take comfort in that. I think Achilles is a real injury that you don’t want to play with, because it’s not good if it gets worse. I think it’s one of the worst.”
The French Open was originally scheduled to start in May, but moved to a starting date in September amid the coronavirus pandemic.
Williams’ retirement means her next chance to catch Margaret Court’s record of 24 specialties will be the Australian Open, which is set to begin in January.