The 42-year-old Cora is a busy man as he finishes up his role as bench coach of the Houston Astros. He agreed to a three-year contract plus a club option for 2021, according to president of baseball operations Dave Dombrowski.
A formal press conference will be held following the World Series between the Astros and Los Angeles Dodgers.
Cora, a native of Puerto Rico, played parts of four seasons with the Red Sox (2005-08) during his 14 seasons as a player. This season's stint with the Astros was his first on a major league coaching staff.
"I am extremely honored and humbled to be named manager of the Boston Red Sox and I want to thank Dave, John Henry, Tom Werner, and Sam Kennedy for giving me such a tremendous opportunity," Cora said of the franchise's upper management in a statement. "Returning to the Red Sox and the city of Boston is a dream come true for me and my family and I look forward to working towards the ultimate goal of winning another championship for this city and its great fans.
"At the same time, I want to express my appreciation for Jim Crane, Jeff Luhnow, A.J. Hinch, and the entire Houston Astros organization for giving me the chance to start my coaching career. It has been a very special season and an incredible organization to be a part of and I am looking forward to the World Series and winning with this group."
Cora, who replaces John Farrell, is the 47th manager in Red Sox history and the 22nd former Boston player to serve in the role. The most recent was Butch Hobson, who served as manager from 1992-94. Cora was also a member of Boston's 2007 World Series championship team.
Cora's stock rose greatly due to the success of the Astros. The club went 101-61 in the regular season and defeated the Red Sox in the American League Division Series and the New York Yankees in the AL Championship Series to reach the World Series for the second time in club history.
"We were very impressed when we interviewed Alex," Dombrowski said in a statement. "He came to us as a highly regarded candidate, and from speaking with him throughout this process, we found him to be very knowledgeable, driven, and deserving of this opportunity. He is a highly respected and hardworking individual who has experience playing in Boston.
"Alex also has a full appreciation for the use of analytical information in today's game and his ability to communicate and relate to both young players and veterans is a plus. Finally, the fact that he is bilingual is very significant for our club."
Cora served as a baseball analyst for four seasons (2013-16) before being hired by the Astros. His varied background and ability to relate to young players was a key in the hiring.
"In Alex we have found a natural leader to guide our clubhouse," Henry, the Red Sox principal owner, said in a statement. "He is extremely smart with a dedication to what it takes to be successful in today's game on the field. His baseball acumen and his ability to think strategically are uncommon for someone his age. We could not have found a better match for our players, our front office and for where we intend to go over the coming years as an organization."
Cora batted .243 in 1,273 big league games from 1998-2011 with the Los Angeles Dodgers (1998-2004), Cleveland Indians (2005), Red Sox, New York (2009-10), Texas Rangers (2010) and Washington Nationals (2011).