By Nick Mulvenney

RIO DE JANEIRO (Reuters) - Poland's Anita Wlodarczyk underlined her absolute dominance of the women's hammer by throwing a world record 82.29 metres to win the Rio Olympic gold by an incredible 554 centimetres on Monday.

The only woman to have thrown the hammer further than 80 metres, the 31-year-old world champion had already broken the Olympic record with a second throw of 80.40 when she entered the ring for the third time.

Whipping the hammer around her body eight times before launching it into the sunny morning sky, Wlodarczyk was screaming in delight before the ball even pitched on the grass of the infield, well beyond the 80 metre tape.

It was far enough to better the mark of 81.08 she set in Cetniewo in Poland this month, as was her fifth throw of 81.74.

"Competition of my life," she told Poland's TVP. "After the first round I knew that I would get the gold medal and after the second one I went for it all. Massacre.

"I think that no one made such a surprise during Olympics. I was close to beating the record for the second time. I didn't want to hold back.

"I thought, this is that day. It was worth giving it a go, because you never know if it's going to happen again - parents in the stands, fans cheering ... I think I'm the happiest woman in the world right now."

Unbeaten since June 2014, Wlodarczyk now owns the 11 best throws of all time. Her winning margin was by far the largest in the history of the women's event.

She was the second Pole to win the title after Kamila Skolimowska, who won the inaugural women's hammer at the Sydney Olympics in 2000 before dying at the age of 26 of a pulmonary embolism while training.

"Everyone thought I'd win the gold medal," said Wlodarczyk. "But the best thing for me is the world record, because I talked a lot about it.

"I didn't fail the fans, I didn't fail Poland so that's just great. It's time to celebrate."

Wlodarczyk finished runner-up to Tatyana Lysenko at the London Games four years ago but the Russian was unable to defend her title in Rio after being banned for doping for the second time in her career earlier this year.

China's Zhang Wenxiu threw 76.75 to add a silver medal to the bronze she won on home soil at the 2008 Beijing Olympics.

Former world junior champion Sophie Hitchon was third with a British record 74.54 from her final throw to claim a first medal for her country in the women's hammer.

"To get a bronze medal, I am over the moon. I didn't expect that I would hold third, I just wanted to throw further," the comparatively diminutive Hitchon said.

"I had to double take a little bit. It was just incredible to see the number three there and a national record, I couldn't be happier."

Betty Heidler of Germany, the 32-year-old former world champion and world record holder, finished fourth with a best throw of 73.71.

(Reporting by Nick Mulvenney Editing by Alison Williams)