Katharine McPhee flashed some serious sideboob at the 2013 Golden Globes last night. Katharine McPhee, "Smash" star and "American Idol" runner-up, posed on the red carpet in a plunging black dress that revealed possibly a little too much cleavage.

Katharine McPhee wore a Theysken's Theory gown with a high-slit, and some of the photos taken of her revealed a side of her rarely seen. Flashing some serious sideboob, Katharine McPhee told E!'s Ryan Seacrest that she wanted to wear something "sexy."

"You've accomplished sexy," Seacrest said to Katharine McPhee, according to Yahoo! News.

Katharine McPhee recently opened up to US Magazine, and spoke about how she shied away from sexy on the "American Idol" set.

"On Idol, I was very strategic with my look," she said, according to US Magazine. "I specifically wore very little makeup, did very little with my hair, I wore beat-up jeans and a simple jacket, and I covered my body up because I knew that viewers like seeing transformation ... I wanted to create that story -- actually to push the story that I had no idea about fashion -- which was not actually true."