A spokesman for Bono, born a girl to Sonny and Cher, says he "has made the courageous decision to honor his true identity" and began the sex-change process earlier this year.
Publicist Howard Bragman said Bono is proud of his decision and hopes "that his choice to transition will open the hearts and minds of the public regarding this issue."
The 40-year-old writer, reality-TV star and activist came out as gay 20 years ago, Bragman said.
"The self-proclaimed tomboy inherited (his parents') musical genes," notes CBS News correspondent Ben Tracy, "but eventually decided to become a prominent activist for gay and lesbian causes after coming out to Mom and Dad at the age of 18."
In the book "Family Outing: A Guide to the Coming-Out Process for Gays, Lesbians, & Their Families," Bono describes the realization of being "somehow different - specifically different from who my mom expected me to be."
A message left with Cher's representatives was not immediately
When Sonny Bono died in a skiing accident, Chastity Bono expressed remorse that their relationship had become straied after Sonny, a U.S. congressman, voted for a bill against same-sex marriages, correspondent Tracy points out.
Bono's second book, "The End of Innocence: A Memoir," details
how relationships with Joan, a lover, and Sonny and Cher changed
after coming out.
In 1995, Bono posed for the cover of the gay magazine The Advocate and began working for the Gay and Lesbian Alliance Against Defamation (GLAAD).