The 33-year-old played a leading role in Japan's success at the 2011 Women's World Cup and adds the Fifa prize to the tournament's Golden Boot and Golden Ball honours.
Sawa dethroned Brazil's Marta, who had won the award for the last five years, with Abby Wambach from the USA coming in third place.
Meanwhile, Japan head coach Norio Sasaki secured the title for the best trainer of 2011 for women's football category, ahead of the USA national team's Pia Sundhage and France's Bruno Bini.
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