Ronda Rousey remains undefeated. And we're talking beyond the Octagon here.

The UFC bantamweight champion received 52 percent of the vote to beat Serena Williams in the final of the Best Female Athlete Bracket. More than 13,000 votes were cast in the final matchup.

Williams, the No. 1 seed, beat Cheryl Miller, the team of Kerri Walsh Jennings and Misty May-Treanor, Babe Didrikson Zaharias and Steffi Graf to reach the final.

Rousey, unseeded, took down Missy Franklin, Jackie Joyner-Kersee, Diana Taurasi and Florence Griffith Joyner before topping Williams.

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Finals

One works her magic on the tennis court, the other in the Octagon. Both fill their opponents with dread and their fans with wonder.

It's top-seeded Serena Williams vs. unseeded Ronda Rousey in the finals of the Best Female Athlete Bracket.

Both women have sailed through the competition so far. Williams has dispatched the likes of Steffi Graf, Cheryl Miller and Babe Didrikson Zaharias. Rousey has cruised past champions such as Jackie Joyner-Kersee, Diana Taurasi and Florence Griffith Joyner.

Now only one can win, and you get to decide.

Ronda Rousey remains undefeated. And we're talking beyond the Octagon here.

The UFC bantamweight champion received 52 percent of the vote to beat Serena Williams in the final of the Best Female Athlete Bracket. More than 13,000 votes were cast in the final matchup.

Williams, the No. 1 seed, beat Cheryl Miller, the team of Kerri Walsh Jennings and Misty May-Treanor, Babe Didrikson Zaharias and Steffi Graf to reach the final.

Rousey, unseeded, took down Missy Franklin, Jackie Joyner-Kersee, Diana Taurasi and Florence Griffith Joyner before topping Williams.

Serena Williams, tennis, vs. Ronda Rousey, MMA

(Athlete bios by Harold Gutmann)

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Semifinals

The question has been debated all summer long. From country clubs to barrooms, from city streets to living rooms, from London to New York. And now you get to answer. Who's a better athlete: Serena Williams or Steffi Graf?

The tennis legends -- Williams the owner of 21 Grand Slam titles and still going strong at age 33, and Graf the owner of 22 Grand Slam titles and retired since 1999 at the age of 30 -- have advanced to the semifinals in our Best Female Athlete Bracket.

The winner will take on either MMA superstar Ronda Rousey, who knocked out No. 2 seed Diana Taurasi in the quarterfinals, or track legend Florence Griffith Joyner, who blew past Lisa Leslie, in the final.

Voting is now open. Click on the images below to lock in your answers.

Serena Williams, tennis, vs. Steffi Graf, tennis

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Ronda Rousey, MMA, vs. Florence Griffith Joyner, track

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Quarterfinals

As the US Open opens today in Flushing Meadows with 128 women in the singles draw, voting in the espnW Best Female Athlete bracket continues with just eight women remaining.

Did we mention that three of them are tennis players? Serena Williams, Steffi Graf and Martina Navratilova join Babe Didrikson Zaharias, Diana Taurasi, Ronda Rousey, Lisa Leslie and Florence Griffith Joyner in the quarterfinals.

Brace yourself. Some of these matchups are doozies. Click on the images to make your picks. Voting is open now.

Serena Williams, tennis, vs. Babe Didrikson Zaharias, multiple

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Steffi Graf, tennis, vs. Martina Navratilova, tennis

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Diana Taurasi, basketball, vs. Ronda Rousey, MMA

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Lisa Leslie, basketball, vs. Florence Griffith Joyner, track

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Round of 16

Knock, knock.

Two seeded contenders were shown the door in the first round of our Best Female Athlete bracket.

So long to basketball players Cynthia Cooper, the No. 4 seed, and Sheryl Swoopes, the No. 6 seed. In fact, of the eight hoops stars in the 32-athlete field, voters sent only two -- Diana Taurasi and Lisa Leslie -- into the Sweet 16.

So who else made it?

Tennis players, headlined by top-seeded and Grand Slam-seeking Serena Williams, went 4-for-4 in Round 1. And three soccer players -- Michelle Akers, Abby Wambach and Mia Hamm -- all rolled on.

The choices only get tougher from here. Sweet 16 voting is open now. Click on the images below to make your picks.

Serena Williams, tennis, vs. Kerri Walsh Jennings and Misty May-Treanor, volleyball

Athlete bios by Harold Gutmann

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Babe Didrikson Zaharias, multiple, vs. Abby Wambach, soccer

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Natalie Coughlin, swimming, vs. Steffi Graf, tennis

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Mia Hamm, soccer, vs. Martina Navratilova, tennis

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Diana Taurasi, basketball, vs. Billie Jean King, tennis

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Ronda Rousey, MMA, vs. Jackie Joyner-Kersee, track

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Michelle Akers, soccer, vs. Lisa Leslie, basketball

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Nadia Comaneci, gymnastics, vs. Florence Griffith Joyner, track

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Round of 32

A whole lot of superlatives have been shadowing Serena Williams this summer. And as the spotlight gets brighter still at the US Open, where the 33-year-old American tennis icon goes for the calendar Grand Slam and major No. 22, one question burns brightest.

Is Serena Williams the best female athlete of all time?

You get to provide the answer.

Between now and the final at Flushing Meadows, 32 of the all-time greats go head-to-head in our Best Female Athlete bracket. Choose between legends such as Wilma Rudolph, Babe Didrikson Zaharias and Florence Griffith Joyner, as well as current stars like Ronda Rousey, Missy Franklin and Maya Moore.

We had some fun -- because what else could it be but fun to compare athletes from different eras (short shorts versus long shorts) and different sports (frontside 1080 versus 14-second armbar)? -- and named eight seeds and drew the rest of the slots.

Polls are officially open. Click the images below for more details on the matchups and vote for the first-round winners.

Serena Williams, tennis, vs. Cheryl Miller, basketball

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Bonnie Blair, speedskating, vs. Kerri Walsh Jennings and Misty May-Treanor, volleyball

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Babe Didrikson Zaharias, multiple, vs. Marta, soccer

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Abby Wambach, soccer, vs. Danica Patrick, auto racing

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Cynthia Cooper, basketball, vs. Natalie Coughlin, swimming

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Steffi Graf, tennis, vs. Lauren Jackson, basketball

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Annika Sorenstam, golf, vs. Mia Hamm, soccer

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Martina Navratilova, tennis, vs. Tamika Catchings, basketball

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Diana Taurasi, basketball, vs. Kelly Clark, snowboarding

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Billie Jean King, tennis, vs. Wilma Rudolph, track

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Ronda Rousey, MMA, vs. Missy Franklin, swimming

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Jackie Joyner-Kersee, track, vs. Hope Solo, soccer

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Michelle Akers, soccer, vs. Maya Moore, basketball

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Lisa Leslie, basketball, vs. Lindsey Vonn, skiing

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Nadia Comaneci, gymnastics, vs. Lisa Fernandez, softball

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Sheryl Swoopes, basketball, vs. Florence Griffith Joyner, track