The world on Monday mourned the death of David Bowie, the iconic rock star, record producer, artist, and performer whose influence spanned generations and whose ideas constantly pushed boundaries of creativity, sexuality, and custom.

Bowie's death was confirmed by a post on his Facebook page, which said that the artist died peacefully in New York City on Sunday "surrounded by his family after a courageous 18 month battle with cancer." He had just celebrated his 69th birthday on January 8.

Bowie, born David Robert Jones in Brixton, south London, was lauded as a performer who was always ahead of his time.

Known best for pioneering the glam rock genre and for hit songs including "Fame," "Let's Dance," "Starman," and "Life on Mars," Bowie's career lasted nearly four decades. In fact, his death came just two days after the release of his most recent album, Blackstar.

Throughout his career, Bowie sold an estimated 140 million albums. In 2004, Rolling Stone magazine ranked him 39th on their list of the 100 Great Rock Artists of All Time. He also had a notable acting career, with memorable roles in films such as 1976's "The Man Who Fell to Earth," and "Labyrinth" in 1986.

In addition to his artistic prowess, Bowie was known as a champion of the underdog. He famously rejected knighthood in 2003 and declined the royal honor of Commander of the Order of the British Empire (CBE) in 2000, saying: "I would never have any intention of accepting anything like that. I seriously don’t know what it’s for. It’s not what I spent my life working for."

In 1972, Bowie introduced his flamboyant, androgynous alter ego Ziggy Stardust, which brought notions of gender fluidity and bisexuality into mainstream popular culture.

"He was a megastar, but his power came from the fact he was the champion of the outcast in the bedroom," wrote British artist Grayson Perry on Monday. "The loner, the misfit. Although I couldn’t afford to buy records then, I absorbed him through TV and radio. The performance of Starman on Top of the Pops, with Bowie rubbing up against Mick Ronson dressed in a spangly catsuit—that was really bringing gender subversion into the mainstream."

In a blog post following news of his death, comedian and author Sara Benincasa wrote that Bowie "was the patron saint of all my favorite fellow travelers: the freaks, the fags, the dykes, the queers, the weirdos of all stripes, and that most dangerous creature of all: the artist."

"He was the crown prince(ss) of the unusual," she continued. "He was so marvelously, spectacularly weird, and he gave so many oddballs, including this one, hope...Goodbye, you beautiful sexy gender-resistant oddball space hero. You gave the weird kids something to aspire to and dream about. We were very lucky to have you in any form, at all, ever, for as long as we got you. Thank you."

Indeed, Bowie said during a rare 2002 interview, "My entire career, I’ve only really worked with the same subject matter. The trousers may change, but the actual words and subjects I’ve always chosen to write with are things to do with isolation, abandonment, fear and anxiety, all of the high points of one’s life."

Lesser known was Bowie's pioneering in the digital realm. Recognizing the vast potential of the internet space, the musician released the first major, downloadable single—1996's "Telling Lies"—and in 1998, Bowie set up his own Internet Service Provider (ISP).

Monday saw an outpouring of love from Bowie's friends and fans. Mourners erected a shrine near his birthplace in Brixton while others expressed condolences online.

Musician Iggy Pop wrote, "David’s friendship was the light of my life. I never met such a brilliant person. He was the best there is." Madonna said that the artist "changed her life."

Bowie leaves behind his wife, Iman, their daughter, Lexi, his stepdaughter, Zulekha, and his son, Duncan, from his first marriage.

"I'm not a prophet or a stone aged man, just a mortal with potential of a superman," Bowie once sang in "Quicksand," realsed in 1971. "I'm living on."