At 6-1 and 1-0 up with a break, Henin, who started the match as the 1/20 favourite, was backed at the minimum odds of 1/100 on Betfair.
An amazing £447,574 was matched on Henin at 1/100, with £797,119 at 1/50, and a further £809,490 at 1/33.
In total over £4m was matched on Henin at 1/20 or shorter.
Betfair spokesman Tony Calvin said: "Winners at the maximum price of 999/1 are regular occurrences on Betfair these days, but I have never seen anything like this.
"Those who backed Henin at 1/100 may be devastated, but the Betfair punters who laid them the bets have effectively backed a 100/1 winner in a two-runner race.
"But even that was eclipsed by those who secured odds of up to 129/1 about Bartoli."
An amazing £447,574 was matched on Henin at 1/100, with £797,119 at 1/50, and a further £809,490 at 1/33.
In total over £4m was matched on Henin at 1/20 or shorter.
Betfair spokesman Tony Calvin said: "Winners at the maximum price of 999/1 are regular occurrences on Betfair these days, but I have never seen anything like this.
"Those who backed Henin at 1/100 may be devastated, but the Betfair punters who laid them the bets have effectively backed a 100/1 winner in a two-runner race.
"But even that was eclipsed by those who secured odds of up to 129/1 about Bartoli."
