The official decision, made before an estimated worldwide viewing audience of some one billion people, was made at the luxury Atlantis Resort by a 12-person judging panel that included Andre Leon Talley, the editor-at-large for American Vogue, actor Dean Cain and supermodel Valeria Mazza.
Two other women from Latin America made it into the top five: 23-year-old Ada de la Cruz of the Dominican Republic and Mayra Matos, 20, of Puerto Rico.
The top group also included contestants from Australia and Kosovo.
As the new Miss Universe, Fernandez will receive a monetary prize, the size of which has been kept confidential.
The top award also includes a 100,000-dollar scholarship to study acting at an academy in New York, a five-day vacation package in the Bahamas for two, a set of jewelry and a complete wardrobe.
The main attraction for contestants is an opportunity to break into and establish themselves in the lucrative world of show business, organizers said.
"Women who seek the title of Miss Universe are driven by their desires to open for themselves new opportunities in the world of acting and entertainment," Acirema Alayeto, president of Miss Latin America Organization, told AFP.
Each contestant was judged in three categories: swimsuit, evening gown and interview as they vied for the coveted title.
For the past two weeks, the women have been touring the various islands and participating in preliminary legs of the competition including the swimsuit presentation in Grand Bahama, a costume presentation, a fashion showcase featuring local designs and fabrics and a state auction dinner in New Providence.
The contestants have also toured other Bahamian islands, including Grand Bahama, Bimini, Exuma, Eleuthera and Abaco, visiting landmarks and posing for photographs.
As Hurricane Bill neared last week, several contestants expressed worries about their safety and the prospects for the competition, but the storm's path passed far away from the islands.
The final event was hosted by Celebrity Apprentice star Claudia Jordan and Access Hollywood co-anchor Billy Bush, and included performances by rapper Flo Rida, singers David Guetta and Kelly Rowland and reality star Heidi Montag.
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