A sex symbol is a famous and/or notable person, male or female, who is found sexually attractive by the general audience.

Sources
The film industry played an important part in the rise of sex symbols. It disseminated images of beautiful people around the world, especially during film's silent era, when there were no language barriers.
The first sex symbols were Danish actress Asta Nielsen (nicknamed 'The Silent Muse'), and 'It Girl' Clara Bow in the 1910s and 1920s. Although not seen as a real sex symbol, Lillian Gish ('The First Lady of the Silent Screen') became the most popular actress of the era. Theda Bara and Pola Negri, famed for their vamp roles, were also early female sex symbols. Rudolph Valentino became the first male sex symbol.
Film's Golden Age sex symbols include 1930s stars Marlene Dietrich, Greta Garbo, Jean Harlow (the 'Platinum Blonde'), Mae West and Clark Gable. 40's and 50's icons Brigitte Bardot, Diana Dors, Ava Gardner, Betty Grable, Rita Hayworth, Audrey Hepburn, Veronica Lake, Sophia Loren, Jayne Mansfield, Marilyn Monroe, Kim Novak, Jane Russell, Elizabeth Taylor, Lana Turner, Mamie Van Doren, Marlon Brando, James Dean, Rock Hudson and Robert Mitchum.
Important 60's and 70's sex symbols included Ann-Margret, Jacqueline Bisset, Barbara Bouchet, Jane Fonda, Pam Grier, Ali MacGraw, Sharon Tate, Raquel Welch, Sean Connery, Steve McQueen, Paul Newman, Robert Redford, Burt Reynolds, Arnold Schwarzenegger and John Travolta.
As TV's influence grew during the last three decades there was a slight shift to TV stars becoming more famous, Pamela Anderson, Tiffani-Amber Thiessen, Carmen Electra, Farrah Fawcett, Jennifer Garner, and Don Johnson, all became sex symbols through TV.
More recent silver screen icons are Jessica Alba, Jennifer Aniston, Halle Berry, Scarlett Johansson, Angelina Jolie, Orlando Bloom, George Clooney, and Brad Pitt.

Film
1930's cartoon character Betty Boop was considered to be a sex symbol. [1]

Cartoons
Rock and roll music also played a part in the introduction of sex symbols to pop culture. Classic examples, such as The Beatles, Jimi Hendrix, Michael Jackson, Mick Jagger, Tom Jones, Jim Morrison, Elvis Presley, Prince, Grace Slick, Bruce Springsteen, Rod Stewart and Steven Tyler set the stage for contemporary examples, such as Justin Timberlake, Marky Mark and LL Cool J. Popular sex symbols include: Ciara,Christina Aguilera, Beyoncé, Toni Braxton, Cher, Janet Jackson, Madonna, Kylie Minogue, Shakira, Britney Spears and The Pussycat Dolls.

Music
Recently, video games have had a few "sex symbol" characters as well. Some examples of this category would be Lara Croft, Tifa Lockhart, Mona Sax, Cortana, Rayne and Rikku.

Teen idols
People magazine, Sexiest Man Alive