We know their names by their Olympic feats. However, these world-class athletes have other monikers that define them. Can you guess the nicknames of these Olympians?

Michael Phelps' speed in the water has helped earn him an impressive number (how many?) of Olympic medals (which athlete has the most Olympic medals?). Will another blistering Summer Games performance help the US swimmer (watch him compete) live up to his nickname?

What's his nickname?

Even though the record-holding (how many Olympic golds has he won?) Australian swimmer won't make an appearance at the London Games (read why he won't compete), here's hoping Ian Thorpe (see photos) can continue to live up to his moniker.

What's his nickname?

A standout at the 1992 and 1996 Summer Olympics, Alexander Popov showed speed in the pool that earned him several gold medals (what were his record-breaking events?) and the distinction of being one of the greatest swimming sprinters of all time (he was the first to tie this swimmer's longstanding record).

His apt moniker?

After stellar gold medal-winning performances (what is her Olympic distinction?) in Athens and Beijing, Chinese diver Guo Jingjing (watch her Olympic form) announced her retirement from the sporting world in 2011.

What is her nickname?

It's not often an Olympian earns a nickname celebrating a third-place win, but Slovenia's Merlene Ottey (where was she born?) still can claim Olympic glory with her impressive collection of bronze medals (how many?).

What's her nickname?

Olga Korbut's impressive routines at the 1972 Olympics (watch her compete) made the young Soviet athlete a household name and brought new interest to the sport of gymnastics (who upstaged her at the '76 Olympics?).

What's her nickname?

The 1996 United States Olympic Women's Gymnastics Team (watch them compete) holds the distinction of being the first U.S. team to take home a gold medal in the Women's Team Competition (which member won an individual gold?).

The team's nickname?

Considered "the fastest woman in the world," Griffith-Joyner had a nickname that recognized not her record-setting performances (her record in these events still stands) at the 1988 Summer Games, but her unique and memorable name (read about her untimely death).

What was her nickname?

Long-distance runner Haile Gebrselassie (where is he from?) holds 27 world records and earned two gold medals for his performance (watch his incredible finish at the Sydney Games) in the 10,000m at the Sydney and Atlanta Games.

What's his nickname?

Throughout the 1920s, Finnish track and field athlete Paavo Nurmi (see photos) dominated the Summer Games, winning nine gold medals during the span of his Olympic career (he competed in these Olympic Games).

What was his nickname?

We can't think of a more fitting nickname for this three-time gold medalist (where is he from?), who holds world records in three Olympic track and field events (watch him run).

What's his nickname?

Although she's known more for her prowess on the sand court (watch her), two-time gold medalist Kerri Walsh's nickname pays homage to her daunting height (how tall is she?) and off-court demeanor.

What's her nickname?

This two-time gold medalist (see photos) earned her animal-inspired nickname from the husband of Kerri Walsh, Treanor's beach volleyball partner (who is he?).

What's her nickname?

One look at Phil Dalhausser's frame (how tall is he?) and the genesis of his nickname becomes apparent.

What's his nickname?

Fanny Blankers-Koen (see photos) dominated the 1948 Olympics (her medal haul), but it was her role as a wife and mother that invited her nickname.

What was her nickname?

Gabby Douglas' nickname is fitting given her penchant for flying high on the uneven bars (watch her in flight).

What's her nickname?

Wilma Rudolph (center) tore through the track and field competition in the 1960 Olympics (watch her 100m-dash win) earned her a nickname that is definitely apropos.

What's her nickname?

Carl Lewis' legendary speed (how many Olympic medals did he earn?) was the inspiration for his nickname.

What's his nickname?

After Mary Lou Retton captured gold in the 1984 Olympics in Los Angeles (watch her compete), she became the darling of the public. That makes her nickname very fitting.

What's her nickname?

Eric Moussambani (what country is he from?) caught the public's attention after his famous 100m swim at the 2000 Olympics. His nickname is a moniker that caught on over the years.

What's his nickname?

Mary Meagher's nickname is a nod to her signature stroke (see video).

What's her nickname?