The Ravens will introduce the 45-year-old Philadelphia Eagles secondary coach, who comes from a football family, during a news conference at noon today.
"It's not a well-traveled path, but we'll prove special-teams coordinators can coach," Harbaugh told Philadelphia radio station WIP a half-hour after being hired. "But a football coach is a football coach. I guess the Ravens saw something they liked."
Harbaugh, who was not made available to local reporters yesterday, left in a limousine for Philadelphia and will return today for the news conference.
Considered a dark-horse candidate when the Ravens' search began, Harbaugh impressed team officials with his intense coaching style and magnetic personality.
The hiring of Harbaugh ends the Ravens' 18-day search for a coach. He will become the third coach in Ravens history, replacing Brian Billick, who was fired Dec. 31 after nine seasons with the team.
"We have the head coach, and we're very excited about it," Ravens spokesman Kevin Byrne said.
An NFL source said Harbaugh will sign a four-year deal worth $2 million to $2.5 million a season, typical for a first-year coach.
"They've got a great organization, a tremendous owner, a tremendous general manager and a good football team sitting there right now. I mean, today," Harbaugh told the Delaware County Times in Pennsylvania. "I can't wait to get started. It's an opportunity I want to make the most of. I'm going to do everything possible to be successful."
Owner Steve Bisciotti offered Harbaugh the job at 5:35 p.m. in the team's boardroom in front of the search committee. After Harbaugh accepted, Bisciotti called former majority owner Art Modell so that he could be one of the first to know.
Harbaugh, the NFL's ninth-youngest head coach, is eight years younger than Billick, which Ravens center Mike Flynn said shouldn't be a problem.
"It's not going to matter," Flynn said. "He's ready for the job. I'm sure he's going to do his homework and will establish his philosophy. ... I think he'll have instant credibility and respect. It's something he would have to lose."
The Ravens will fly Harbaugh's parents to Baltimore for the official announcement.
His father, Jack, a 41-year coaching veteran, was head coach at Western Kentucky University when the team won the 2002 Division I-AA national championship.
Harbaugh's brother, Jim, the Ravens' quarterback in 1998, is now head coach at Stanford University.
The Ravens first targeted Dallas Cowboys offensive coordinator Jason Garrett and tried to hire him during a seven-hour visit Tuesday. Garrett turned down the Ravens' offer Thursday and decided to remain with Dallas.
Harbaugh, who was considered the fallback if Garrett wasn't hired, was the second candidate to be interviewed twice, arriving at Ravens headquarters about 9 a.m. yesterday
He doesn't have credentials typical of some other head coach candidates but has been considered by several NFL teams. A high-ranking Ravens official said last year that Harbaugh would be an excellent head coach.
Harbaugh was a finalist for the UCLA job last month and for the Miami Dolphins' opening last year.
"He always aspired to be something more than a special-teams coordinator," said former Eagles linebacker Ike Reese, whom the Ravens' search committee contacted as part of its evaluation. "He always felt he brought more insight to the game of football, and he wanted to ultimately be a head coach. I'll be pulling for him. I'm an immediate Ravens fan."
Harbaugh has built a reputation as an energetic teacher who gets the most out of his players.
He shifted to secondary coach this season to give himself a better chance to become a head coach. He had spent the previous nine seasons coaching the Eagles' special teams. Before joining Philadelphia's staff, Harbaugh held a variety of college jobs for 13 years.
"I couldn't be happier for John and his entire family," Eagles head coach Andy Reid said. "He has worked very hard to become a head coach in the National Football League. I know how much this means to him. He is very deserving of this opportunity, and we will miss him in Philadelphia. I wish him all the best in Baltimore."
Others interviewed by the Ravens were former Ravens defensive coordinator Rex Ryan; Dallas Cowboys assistant head coach Tony Sparano, who was hired by the Miami Dolphins; New York Jets offensive coordinator Brian Schottenheimer; and Indianapolis Colts assistant head coach Jim Caldwell, who withdrew.
"When you're in this process of finding a head coach, you're kind of in limbo as a team," Ravens tight end Todd Heap said. "Now, we can finally go forward. It's going to be an exciting time."