She's one of the biggest artists on the planet, so it's no surprise that Britney Spears is performing at the 2015 Billboard Music Awards. This also happens to be the award show where she loves to share the stage with fellow pop stars, which is why Spears is bringing along rapper Iggy Azalea to perform their latest single "Pretty Girls." Based on the song's '80s throwback style music video, fans are curious to see if Spears will go retro for the red carpet and her stage performance. After all, the singer has worn some of her most memorable outfits at the Billboard Music Awards.

Even though she hasn't experimented with her looks as drastically as other pop stars, Spears' style evolution has come a long way ever since her first Billboard awards appearance in 1999, wearing a pastel gown with white shawl. She played up her "I'm not that innocent" mantra the following year with a bright orange and pink ensemble, with matching feathered hat. In 2004, Spears wore a lace mini and brought along her then-husband Kevin Federline and one of her chihuahuas to the carpet. Due to her health and personal issues, Spears did not appear at the BBMAs for several years, but she made a huge comeback in 2011 with two unforgettable performances — and outfits — alongside Rihanna and Nicki Minaj.

Of course, Spears wasn't just there to perform. Throughout her career, she has won seven Billboard Music Awards, including New Artist of the Year, Female Artist of the Year, Female Albums Artist of the Year, and Female Singles Artist of the Year in 1999. A year later, she picked up Albums Artist of the Year as well as a special recognition for the highest first week sales ever for a female artist. Spears won again in 2004 for Hot Dance Sales Singles of the Year, an honor she shared with her idol Madonna for their hit duet "Me Against the Music."

In honor of her upcoming appearance on Sunday, I'm doing a run down of Britney Spears' Billboard Music Awards outfits, ranked from least memorable to totally fierce:

8. Lovely in Lace, 2004

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Spears definitely rocked this nude illusion mini at the 2004 BBMAs, but she's had better fashion moments.

7. Back in Black, 2011

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Spears came out to surprise the audience (her second performance that night) at the end of Nicki Minaj's set for a remix of "Till The World Ends." Her outfit was fine, but simply didn't match up to the rapper's fun, avant-garde ensemble.

6. Fierce In Fringe, 1999

One could definitely argue that Spears was responsible for making fringe happen.

5. Zoot Suit Riot, 2000

Although this sexy Zoot suit looks completely outdated, this was Spears at her pop princess peak (during the time when everything she wore matched).

4. Glam Goddess, 1999

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Like a princess at her first ball, Spears looked radiant in a lilac gown arriving on the 1999 BBMAs red carpet.

3. I'm A Slave 4 U, 2001

Brit was definitely at the top of her game during her "I'm A Slave 4 U" phase.

2. Sugar and Spice, 2011

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Spears made a cameo during Rihanna's opening number to perform the "S&M" remix. Decked in all-black bondage gear and bunny mask, the look was fashionably naughty and classic Britney.

1. Because Rihanna

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The aftermath of the world's most epic pillow fight.

Images: Getty (6)