Serena Williams has crushed Caroline Wozniacki in straight sets to become the first woman in almost 40 years to complete a US Open title hat-trick.

The world No.1 blasted 29 winners in her 6-3 6-3 victory to land her sixth Open crown and draw level with fellow American greats Martina Navratilova and Chris Evert on the all-time grand slam leaderboard.

Williams’ 18 majors elevates the 32-year-old to equal fourth place behind Australia’s record holder Margaret Smith Court, who won 24 grand slam singles titles, Steffi Graf (22) and Helen Wills Moody (19).

After failing to progress beyond the last 16 at the season’s first three grand slam events in Melbourne, Paris and London, Williams was on a mission on Sunday.

So dominant was she that Wozniacki could only manage four winners against the single-minded top seed.

And three of those were aces.

The Dane was only able to conjure one winner from the back of the court, surviving only Williams errors.

After breaking Wozniacki three times to take the opening set, Williams continued the onslaught with an early break in the second.

The world No.11 never came close to breaking back and the match was all over after one hour and 15 minutes as Williams became the first woman since Evert, who won four straight titles from 1975-78, to complete an Open hat-trick.

In addition to the grand slam spoils, the triumph earned Williams the biggest cheque in tennis history, a whopping $US4 million ($A4.33 million), including a $US1 million bonus for also winning the US Open summer series.

For Wozniacki, it was her second finals defeat in New York after the former world No.1 lost the 2009 decider to Kim Clijsters.

After topping the rankings for 67 weeks in 2010 and 2011, Wozniacki retains the tag as the the best player without a grand slam title.