King and ex-Cavaliers GM Danny Ferry were believed to be the two finalists.
"I am very pleased Billy King is coming on board as Nets general manager," Prokhorov said in a statement. "He has all of the qualities we've been looking for in a candidate: professionalism; good relations with the league, players and agents; and strong communications skills.
"He will be an excellent fit with head coach Avery Johnson. Most importantly, Billy is ambitious. He wants to win. This is what I felt when I met with him and why he will be a strong addition to the Nets organization."
King, 44, who played college basketball at Duke, was the 76ers' top personnel man for nearly 10 years before being fired in the 2007-08 season. He was promoted to team president in 2003, two years after his Allen Iverson-led Sixers reached the NBA Finals. Philadelphia made four other playoff appearances during his tenure.
"I am very excited about joining the Nets organization," King said in a statement. "I want to thank Mr. Prokhorov and his executive team for the opportunity to oversee a franchise that has such a vibrant owner, an outstanding coach in Avery Johnson, and possesses the combination of young talent, cap space, and draft choices that will allow us to build a squad that will be able to contend for an NBA title."
King joins a club that needs help everywhere and has been hoping to lure a big-name free agent with the $14 million it has remaining in salary-cap space. But now that LeBron James, Dwyane Wade, and Chris Bosh have signed with Miami, Prokhorov has said it's time to implement Plan B.
