The England and Wales Cricket Board confirmed on Tuesday that Pietersen had not been selected for England's squads for the upcoming limited-overs tour of the West Indies and March's ICC World Twenty20 in Bangladesh.
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The announcement comes after a meeting between the 33-year-old and ECB managing director Paul Downton earlier this week, in which Pietersen was informed that the England management had decided unanimously that he would not be part of the team moving forward.
And Pietersen, who is England's record international run scorer, has expressed his regret, while indicating that he has played his final match for his country.
"Playing cricket for my country has been a huge honour," said the batsman.
"Every time I pulled on the England shirt was a moment of huge pride for me and that is something that will live with me forever.
"Although I am obviously very sad the incredible journey has come to an end, I'm also hugely proud of what we, as a team, have achieved over the past nine years.
"I feel extremely fortunate to have played at a time of great success for England cricket alongside some of the best cricketers the country has ever produced.
"I want to thank everyone for their fantastic support and I wish the team the very best of success going forward.
"I believe I have a great deal to give as a cricketer. I will continue to play but deeply regret that it won't be for England."
Pietersen has played in 104 Test matches, 136 ODIs and 37 Twenty20 internationals for England.
He was at his best in the longest form of the game, scoring 8,181 runs at an average of 47.28, and only one English batsman - current captain Alastair Cook - has scored more Test hundreds than his 23.