It wasn’t noticed much by soccer-phobic U.S. media.

But a study put out earlier this year by German sports research firm Sport+Markt found that a full 38 percent of soccer fans worldwide are women.

The study questioned over 20,000 people in 21 countries.

That means millions upon millions of women around the world tuning into soccer games on TV, cheering club and national teams, and purchasing gear, jerseys and fan paraphernalia.

According to a story by Reuters on the study, “over a third of people interested in the (British) Premier League are female with Chinese women having a particular high interest in English soccer.”

The implications are huge for the world’s most popular sport as it gears up for the 2010 World Cup in South Africa. With many sports trying, and mostly failing, to build interest among women, it appears soccer has a largely untapped female global fan base.

In recent years, stars like Brandi Chastain of the U.S. national team and soccer superstar Marta Vieira da Silva of Brazil have generated enthusiasm for women’s soccer leagues and international championships. It may be that the world’s most popular sport becomes the first one, beyond tennis, to create a truly robust women’s division, in terms of fan interest and sponsorships, the lifebloods of any sport.

Below is a famous goal by Brazil’s hugely talented Marta, scored in the Women’s World Cup against the U.S.A. team (narrated in Portuguese by an obviously pleased Brazilian announcer):

And here she is profiled by the New York Times Magazine, which calls her the “best player in women’s soccer.”