"It's the end of a wonderful adventure but it's something I have been thinking about for a long time," said the 25-year-old, the winner of seven Grand Slam singles titles.
She said that she first thought of quitting in late 2007 and that she had finally decided to do so in Berlin last week, where she was beaten in a match for the place in a quarterfinal by Russia's Dinara Safina in the German Open.
"I'm at the end of the road," said the winner of 41 WTA singles titles, adding that, "This is the end of a child's dream. I have experienced everything I could have. I have lived completely for tennis. I am relieved and proud of what I achieved."
Henin has won the French Open four times, the U.S. Open twice and the Australian Open once.
Henin had the best season of her career in 2007, losing only four out of 67 matches, and winning 10 of the 14 tournaments she took part in. Her winning percentage totaled 94% and is the best in women's tennis since 1989.
She insists she will not go back on her decision.