LOS ANGELES (Reuters) - Pop singer Rihanna was named Woman of the Year by Glamour magazine on Tuesday after an attack at the hands of boyfriend Chris Brown that she said changed her life overnight.

"I went to sleep as Rihanna and woke up as Britney Spears. That was the level of media chaos that happened the next day," the 21 year-old singer said in her first interview since the assault in February.

The R&B singer told the December issue of Glamour magazine that she felt humiliated when a photo of her bruised and bloodied face was leaked to the media, but that she wanted to use the incident to alert young women to the "big secret" of abusive relationships.

"It was humiliating: that is not a photo you would show to anybody," she said. "I felt completely taken advantage of. I felt like people were making it into a fun topic on the Internet, and it's my life.

Brown, 20, was one of the fastest rising young R&B artists in the United States before his assault on his girlfriend of about a year on the eve of the Grammy Awards in Los Angeles.

He was sentenced to five years probation and community service in August and has publicly apologized.

Rihanna, whose hits include "Umbrella" and "Disturbia" said the positive outcome of the story grabbing worldwide attention was that she could now speak up on behalf of young women in similar situations.

"Teenage girls can't tell their parents that their boyfriend beats them up...It's one of the things we (women) hide because it's embarrassing.

"I want to give as much insight as I can to young women because I feel like I represent a voice that isn't really heard. Now I can help speak for those women," she said.

Glamour editor-in-chief Cini Leive said the magazine had chosen Rihanna as its Woman of the Year because "in breaking her silence about what she calls the 'big secret' of domestic violence, she is sending an important message to young women that they too can move on, and succeed after personal challenges."

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Rihanna, who is about to release a new album "Rated R", said she had "put everything I've wanted to say for the past eight months into my music", adding "it's super fearless -- which is exactly how I feel right now."

The album's first single, "Russian Roulette," finds her singing about a tumultuous relationship and ends with an ominous gunshot.

Rihanna has also recorded a TV interview, which is due to be aired on ABC's "Good Morning America" program on Thursday and Friday.

(Reporting by Jill Serjeant; Editing by Bob Tourtellotte)