Happy 25th Birthday Rihanna! See Her Sexiest Looks

Rihanna is celebrating her 25th birthday Wednesday with some fun in the sun in Hawaii, and in honor of the Barbados beauty, RadarOnline.com is giving you a look at some of the singer's sexiest looks over the years.

The stunning S&M singer, who has more than 28 million Twitter followers, tweeted in memory of her late grandmother: "Missing you today especially #grangranDolly my guardian." angel

The Umbrella singer raised eyebrows when she canoodled with sometimes-boyfriend Chris Brown at the Grammys earlier this month, almost four years to the day he viciously beat her up after an argument in Hancock Park, Calif.