Following the announcement, a ninth-inning rally for the Dodgers fell short in a 7-5 loss to the Rockies on Friday night.
General manager Ned Colletti said he was secure enough in Mattingly to give him an unpublicized three-year contract just before this season started, guaranteeing that Mattingly would be Torre's replacement whenever the time came.
Mattingly, 49, was a six-time All-Star and nine-time Gold Glove first baseman for the Yankees, winning the American League Most Valuable Player award in 1985. Among former Yankee players to go on as managers are Lou Piniella, Ralph Houk, Billy Martin, Felipe Alou, Johnny Oates, Joe Girardi, Leo Durocher, Don Baylor, Yogi Berra and Bobby Cox.
Mattingly has never managed at any level, though he will manage in the upcoming Arizona Fall League. When he joined the Dodgers with Torre three years ago, Colletti talked about having a succession plan in place to provide for continuity -- and he has been the heir apparent ever since.
Colletti said he conducted no other interviews and that MLB waived its mandate that minority candidates be interviewed for managerial openings based on the organization's hiring practices of the past.
Team owner Frank McCourt said he had one question for Mattingly.
"Are you ready?" he asked.
"I feel like I'm ready," said Mattingly, who was passed over as Torre's replacement three years ago when the Yankees chose Girardi. "I have confidence in myself. I know people are going to question it. It's understandable. It's a belief in myself."
Mattingly said his style will incorporate managers he served under, from Torre to Martin, Piniella, Dallas Green and Berra.
"But there's only one way to play -- the right way," Mattingly said. "I'll just be myself."
Mattingly will become the Dodgers' seventh manager since Tom Lasorda stepped down in 1996 with health issues. Lasorda had managed the Dodgers for 20 years.
Taking over as hitting coach midway through 2008, Mattingly saw the Dodgers' offense finish first in runs, but he also had the stretch-run infusion of Manny Ramirez's two incredible months of offense.
Last year the Dodgers finished tied for first in the league in runs scored, even though Ramirez missed 50 games with a drug suspension and returned without his legendary power. This year, however, the Dodgers are 12th and have been shut out a league-high 16 times.
"I sabotaged the second half with the offense," Mattingly said. "I apologize for that."
Torre had been negotiating a contract extension with the Dodgers over the winter, but tabled discussions during Spring Training, saying that he wasn't sure whether he wanted to manage after this season or how much of a front office role he might want when he did stop managing.
There have been rumors that Torre might be interested in managing elsewhere. He did little to knock them down.
"I don't anticipate that being the case," he said. "If I say I'd never manage again, that closes the door and makes me feel old. I don't anticipate, but I won't say I'm not going to listen if it's intriguing or exciting."
There also had been reports that Torre became disenchanted with the Dodgers' ownership uncertainty and its impact on player acquisition, as well as feeling pressure from his wife and daughter, who missed their New York roots.
The change comes with Los Angeles (72-75) in fourth place, 11 games behind San Francisco.
Torre has more postseason victories than any other manager in Major League history, ranks fifth on the all-time regular season wins list and has posted a three-year record with the Dodgers of 251-220 (.533) through Thursday night's game.
Torre took over the Dodgers from Grady Little after they finished the 2007 season 82-80, in fourth place. The clubhouse was divided between aging veterans and the young corps of players that became the nucleus for back-to-back division titles.
But most of the young players regressed this year, or at least, were unable to advance their game. Mattingly said he expects them to rebound.
"I've seen them do it in '08 and '09," he said. "I've seen young guys struggle at times, hit a plateau, take a step backward to go forward. All of a sudden they think it's easy and got to get back to work. I've seen it before, so I know it's there."
The status of the coaching staff is uncertain. None is signed beyond this year. Colletti said he won't insist on a coach Mattingly doesn't want, or accept a Mattingly pick that he doesn't want.
Colletti said Mattingly needs an experienced bench coach, but said that didn't necessarily mean a former Major League manager. Larry Bowa is the only member of the current staff with Major League managerial experience.
Triple-A Albuquerque manager Tim Wallach, considered to be a top managerial prospect, is likely to be part of Mattingly's staff, but he was reluctant to talk about it.
"Donnie put in his time, he deserves this," Wallach said. "I am really happy. I put in my time, but this isn't about me. It's about Donnie. He has the knowledge, the temperament, the ability to deal with the players on this level. I haven't thought about this job. I didn't take the Triple-A job to necessarily manage the Dodgers."