The separation comes three days before the release of her newest album, ARTpop, and just two days after a disappointing appearance on the YouTube music awards. In addition, singles from ARTpop released in the last two months have not done as well as hoped.
Exactly why the two have parted is speculative at this point. But it is clear that Carter's interests now extend well beyond Lady Gaga and that her artistic vision and his may no longer be in sync.
With Carter as her manager, Lady Gaga has sold more than 24 million albums and 90 million singles and has become one of the biggest names in pop music.
Her rise was so meteoric that the Harvard Business School has done two case studies - focusing largely on Troy Carter's role as manager.
After a show in January in Los Angeles, Lady Gaga told her fans, "I'd like to thank my music producer, Vince Herbert, and my manager, Troy Carter, for believing in me and taking care of me, so I can travel the world for all my beautiful fans, who I love so much."
Herbert discovered Gaga, born Stefani Germanotta, and recruited Carter, the one-time West Philadelphia High School dropout, to manage her. For years, they were the Three Musketeers, all for one and one for all.
As Herbert said in an Inquirer profile on Carter in February, "We didn't have money for the ideas we wanted. We didn't have people paying attention to us. We had none of that support. But what we had was each other. We had heart."
Carter's success with Gaga gave him means and access to indulge his entrepreneurial flair. In the last few years, he has created what Billboard magazine calls a "mini-empire," teaming with Silicon Valley techies and investors to back more than 40 high-tech start-up companies, from Uber, a site for hiring a private driver, to the music download service Spotify.
According to the technology news site PandoDaily.com, Carter is also raising $75 million to $100 million for an investment fund.
Carter also manages John Legend and violinist Lindsey Stirling - a breakout star on YouTube.
Carter grew up at 52d Street and Larchwood Avenue, in a two-bedroom apartment with kerosene heat and sometimes no running water, he said. His mother proudly says her three boys always had hot meals, love, and high expectations. But Carter recalled the days his mother would scrape together coins for bus fare. "You know, we were broke," he said. "You can, as a kid, kind of recognize the pain in your mother's face."
Carter got his own start as a teenager, sneaking into a recording studio on Delaware Avenue and getting DJ Jazzy Jeff and the Fresh Prince - Jeff Townes and Will Smith, respectively - to listen to his rap group. They loved him, if not his music. He then went to work emptying trash or doing what was necessary for James Lassiter, Smith's longtime manager.
Carter was then on his way, though he had his share of ups and downs, until boarding the Gaga train.
This article contains information from the New York Times, the Associated Press, and other wire reports.