Underwood, 29, who acted as co-host of the show with Brad Paisley, showed some skin in an ivory, chiffon Reem Acra gown on the red carpet. The stunning dress also featured a low-cut, see-through neckline with gold flower applique. The "Blown Away" singer carried a Daniel Swarovski's gold leather Bel Air clutch with crystal closure to accessorize the look.
"Happy CMA day! I woke up early excited thinking about our monologue," Underwood tweeted Thursday. "I think it's going to be a great night!"
Continuing to promote her new album, Red, Swift, 22, wore a stunning nude gown with red floral accents. The "We Are Never Ever Getting Back Together" signer wore Neil Lane diamond and gold cluster earrings and a ruby, moonstone and gold ring. Swift changed into a short, flirty red dress for a performance of her new single, "Begin Again," during the show.
Panettiere, the star of ABC's new hit show, Nashville, looked gorgeous on the red carpet in a Georges Chakra Couture water green Charleston dress, with lines of pearls and fringe on the back. The actress, 23, also styled a L'Dezen Jewellery diamond bracelet. "Going to the CMAs tonight," Panettiere tweeted Thursday. "So excited!"
See what all the stars wore in the gallery and tell Us: Whose CMA ensemble was your favorite?