The choice of Pietersen is a bold move by the selectors
Kevin Pietersen will captain England in the final match of their one-day series against New Zealand on Saturday.
The South Africa-born batting star will take over from Paul Collingwood, who was given a four-match ban because of a slow over-rate during Thursday's match.
Pietersen, who turns 28 on Friday, has been England's unofficial vice-captain in one-day cricket since June 2007.
He said: "Captaining England has been a dream of mine but I understand that I'm assuming the role in Paul's absence."
Saying he was "humbled" by the appointment, Pietersen went on: "To be asked to captain your country is the ultimate honour in sport and I feel privileged and proud.
"I am excited by the challenge of captaining such a young and talented side."
England are 2-1 behind in the five-match series, despite having taken a 1-0 series lead after a memorable Pietersen century at Chester-le-Street.
The new skipper added: "I, like the rest of the dressing room, expect an outstanding England performance to finish the series on a high."
Pietersen qualified to play for England in 2004, and immediately showed his batting prowess on a global level with a series of thrilling performances in a one-day series in South Africa.
The following summer, having switched from Nottinghamshire to Hampshire, he was the leading run-scorer in the famous 2-1 Ashes series win.
He has gone on to record more fabulous innings for England in all forms of the game.
But he is also an outspoken individual, making clear his desire to play in the lucrative Indian Premier League and expressing the view that 50-over cricket would soon be "something of the past".
England's Test captain Michael Vaughan said of Pietersen: "He's thoughtful, his tactics seem pretty good and I'm sure he'll do a good job.
"He has the respect of the players and generally does well on big occasions - and there's no bigger occasion than a Saturday at Lord's with a must-win game at stake.
"He seems to write his own scripts and who's to say he won't get a hundred and England win the match?"
Pietersen will be in line to lead England for three further matches in August, as the team will also require a replacement for Collingwood for those matches.
It is going to be a responsibility that is going to be interesting for him to handle
South Africa captain
They are a one-day international against Scotland on 18 August, a Twenty20 match versus South Africa two days later, and the first of five one-dayers against the same touring side on 22 August.
England have called up Andrew Strauss as cover for the absent Collingwood in the squad for the Lord's match.
But Collingwood is more likely to be replaced by fellow all-rounder, Hampshire's Dimitri Mascarenhas.
On a busy news day for cricket in England, the arrival of Graeme Smith and his South African tourists went by virtually unnoticed.
Smith was labelled "childish" by Pietersen for criticising the South African-born player for switching allegiance to England.
But asked how Pietersen might perform as a captain, Smith was guarded with his views on Thursday.
"It is going to be a responsibility that is going to be interesting for him to handle," he said.
"He is a key player in the set-up and how he handles that is going to be important for him."