Pep Guardiola will stand down as Barcelona manager at the end of the season after deciding not to renew his rolling one-year contract.
The 41-year-old, who was appointed in 2008 and has led the Catalan club to 13 trophies, will be succeeded by current assistant Tito Vilanova.
Barca look set to
miss out to Real Madrid in La Liga
knocked out of the Champions League by Chelsea.
"The reason is simple: four years is enough," said Guardiola.
"I'm drained and I need to fill up. The demand has been very high and a manager must be strong."
Who is new boss Tito Vilanova?
- Francesc 'Tito' Vilanova was a friend of Pep Guardiola at Barcelona's La Masia academy
- After progressing to Barcelona B, the midfielder left the club, spending three years with Celta Vigo
- Following retirement in 2002, the Spaniard joined lower league Barcelona-based side Terrassa FC as technical director
- The 42-year-old was brought back to coach Barca B when Guardiola took control of the side in 2007
- He moved up to the role of Guardiola's assistant coach at Barcelona when Pep moved up to the top job in 2008
It is understood the former Spain international will take a year away from football after relinquishing his duties to Vilanova.
"At the beginning of December I announced to the chairman that I was seeing the end of my era at Barcelona," Guardiola continued.
"Time has taken its toll - I rise each day and don't feel the same. I am going with the understanding that I have done my duty.
"You can only recover by resting and getting away from everything. It would have been a bad idea to continue. Perhaps it would not have gone wrong but I have the perception that it would. It is my time to go.
"Now we are out of the two main competitions it is a good time to announce this. I did not want to continue with the confusion.
"I want to thank my players who are responsible for everything that has happened here. I don't want to manage at the moment."
Guardiola was speaking at a news conference attended by many of his players and received rapturous applause at the end.
"The technical relationships on the pitch are the result of years of indoctrination and feverishly practiced drills. That's exactly why the recapture of Gerard Pique from Manchester United and Cesc Fabregas from Arsenal was so important"
The likes of captain Carles Puyol, Xavi, Andres Iniesta and Cesc Fabregas looked emotional as their coach announced his departure.
Vilanova was not among the favourites to replace Guardiola once it emerged he would be leaving.
But Barca sporting director Andoni Zubizarreta said: "We've always said that if the team needs players, we look at home first. What do we have here at home? Tito.
"We chose Tito because he represents the idea and the image. He has commitment and personality."
Guardiola added: "Barca is making a great choice. He's very capable. The players know him. Even though I won't be here physically - if Tito needs me, I'm here."
Guardiola is the most successful coach in Barca history, with three league titles, two Champions Leagues and a Copa del Rey among his haul.
He has overseen the rise of three-time world player of the year Lionel Messi, Xavi and Iniesta, while
signing Fabregas from Arsenal.
Guardiola was particularly close to Messi -
describing him as "the best ever" player
- while the Argentina forward suggested
Guardiola was the main factor
behind Barca's recent success.
Messi was one of the players who opted to stay away from Guardiola's news conference.
Instead he posted a message on his Facebook page and stated he felt too much emotion to face the media glare.
"Because of the emotions I feel I preferred not to be present at Pep's press conference and to stay away from the press because I know they will look for the pain on the players' faces," said Messi.
"It is something I decided not to show."