Bean -- who served as the league's senior VP for Diversity, Equity, and Inclusion and Special Assistant to the Commissioner -- passed away after a year-long battle with Acute Myeloid Leukemia.

Bean -- one of the first openly gay players in MLB -- was first diagnosed with the disease in September 2023 ... but only went public with the news during the MLB Winter Meetings in December. At the meetings, Arizona Diamondbacks manager Torey Lovullo got emotional when talking about his long-time friend ... saying it was time to help "take care of you."

Bean played seven years in the pros -- including one season in Japan.  After his playing days ... he spent his time working with the league and its 30 teams to work on LGBTQ+ inclusion, social justice initiatives, and player education to bring more equality into the game.

MLB commissioner Rob Manfred released a statement on Bean's passing ... calling him "one of the kindest and most respected individuals I have ever known."

"Billy was a friend to countless people across our game, and he made a difference through his constant dedication to others," Manfred said. "He made Baseball a better institution, both on and off the field, by the power of his example, his empathy, his communication skills, his deep relationships inside and outside the sport, and his commitment to doing the right thing."