Avram Grant will take charge of training for the first time on Friday at Portsmouth knowing he has the backing of the supporters.
The former Chelsea manager replaces Paul Hart, who was sacked on Tuesday with the club rooted to the foot of the Premier League with only seven points from 13 games.
Grant's first match is against a familiar foe in Manchester United at Fratton Park on Saturday.
The Israeli will no doubt be hoping to turn the tables on Sir Alex Ferguson's side as his last game in charge of Chelsea was the Champions League final of 2008. It ended in agony for Grant with his team losing on penalties in Moscow.
Now he is entering a new era and Nigel Tressider, chairman of the official Portsmouth supporters club, welcomed the appointment.
He told Sky Sports News: "It is good for the club. He is very experienced and has the ability. He also has good contacts and knows what he is doing.
"Hopefully the new owners will give him the money for players he needs to strengthen the squad and keep us in the Premier League."
Portsmouth have no doubts Grant can rally the players.
Chief executive officer Peter Storrie said: "Avram is a very experienced and respected manager who has managed at the highest level.
"The board believes he is the man to help steer the club out of the relegation zone.
"He will take charge of training on Friday alongside first-team coaches Paul Groves and Ian Woan."
Former England midfielder Paul Merson, who had a spell at Portsmouth, fears for the club's status.
He said: "I am shocked and surprised. They had a great team spirit even though they were bottom. This could go completely the other way and turn things upside down.
"Paul Hart brought players in, who were out of favour at their clubs, and gave them a second chance. Now he is gone I am worried for Portsmouth. I could see them getting out of trouble, now I am not so sure."
Grant was due to receive his work permit for his director of football role this week and the club have revealed he will at first continue to work in this capacity.
The club will then "go through the process of making the technical change that will allow Avram to become manager".
It adds that this involved "acquiring a new sponsorship number from the Football Association to change his permit status".
Hart, meanwhile, has confirmed he has rejected the club's offer of a return to his former role with the youth set-up.
Pompey chief executive Peter Storrie added: "Avram is taking charge of the team as director of football.
"He will be appointed as and when he receives a change to his work permit - they are the rules and regulations in this country.
"He's not the manager yet - but will become it, which we hope will be next week."
Grant, appointed technical director of Portsmouth in 2006 prior to a spell at Chelsea, continued: "I came here as director of football and I think that's a very important position in clubs.
"I did the job when I came in 2006 - it was good for me and the club, I enjoyed it very much. I came to help the club and I'm happy to do it also now.
"I need to do a good job because the team are not in a good position. I love this club.
"I've have had many situations in my life. Chelsea was different - I went there when they were in a bit of a crisis, they were on the way down - and the result was good in the end."
As for what is needed to keep Pompey up, Grant added: "I think the spirit of the team and the atmosphere are good, they are trying to play good football.
"There have been good results in the last month compared to before...but what's happened has happened and I'm looking forward to the next game (Manchester United at home tomorrow)."
On Hart, the Israeli added: "He did a good job, the situation was not easy."
Chief executive Peter Storrie said Grant was the only candidate given serious consideration for the job.
"You look at the people who are currently out of work and available and in our opinion Avram was head of that list by a million miles," he said.
"We looked at all the names on the list and once it had Avram on it, he's managed a national team, he's managed Chelsea, no-one else came close."
Storrie revealed that club owner Ali Al Faraj has been taking part in board meetings regarding both the sacking of Hart and Grant's appointment as his replacement via conference calls.
"It was a board decision," he said of Hart's departure.
"Paul has done a fantastic job for this club through very difficult circumstances. We feel very sorry, he's been unlucky in certain ways, we've lost so many games by the odd goal.
"Paul leaves here with great dignity and respect. No-one can speak more highly of him than us, and no-one is more disappointed than me that Paul didn't stay on in a very important role (with the youth teams)."
Storrie added that he expects the club's transfer embargo to be lifted in time for the January window and for money to be available.
"Avram will now look at where he thinks we need to strengthen the side," he said.
Grant did not say where that strengthening might come.
He said: "I think the squad is good enough to take us from the bottom, but we need some players who can improve us and also the (African Nations Cup) is coming so some players will not be around for a month and we need to think about that."
Grant's first game in charge will come against Manchester United tomorrow, the same team he faced in his last match as Chelsea boss, when they lost the Champions League final on penalties.
"It won't go to penalties tomorrow," he said with a rueful smile.
"Manchester United are a very good team, they have a great manager who's a very nice person, but we need the points."