5 youngest US Open women's singles champions

#4 Serena Williams

Serena Williams after winning her first Grand Slam title

If Steffi Graf has made the list, then it doesn't seem surprising at all that Serena Williams too makes the list. After all, the two of them are considered among the top-5 greatest tennis players of all time. They share quite a few records -- including holding the WTA top position for a record 186 consecutive weeks.

Serena Williams has won an all time record of 331 matches at the Grand Slam level but her march to higher echelons of greatness began almost 20 years back in 1999. A teenaged prodigy, she came into the US Open as the 7th seed. She won her first two matches comfortably but faced difficulty in the 3rd round and the 4th round, needing to come from a set down on both occasions against Kim Clijsters and Conchita Martinez respectively.

In the quarter-final too, she had to come from a set down to beat Monica Seles. Another 3-set victory against Lindsay Davenport followed in the semis before she prevailed over Martina Hingis in the final in straight sets. Serena Willams was 17 years, 350 days old at the time of winning her first Grand Slam title.