The Post made the announcement on Twitter, referring to the policy analyst simply by his first name.
It's official: Ezra is leaving the Post. Hoping for the best for him.
— Wonkblog (@Wonkblog) January 21, 2014
Klein also took to Twitter to express gratitude to the Post.
Thanks to the @WashingtonPost for five incredible years. An amazing newsroom and an amazing institution.
— Ezra Klein (@ezraklein) January 21, 2014
A report earlier this month indicated that Klein was planning an exit from the Post after he failed to win support from the newspaper's higher-ups for a website dedicated to a range of different topics.
In a memo that was obtained by Poynter, senior editor Tracy Grant told staffers that Klein is "looking to start his own news organization, an ambition that befits someone with uncommon gifts of perception and analysis."
Klein did not immediately respond to TPM's request for comment.
Since arriving at the Post in 2009 at the age of 24, Klein helped turn the newspaper's Wonkblog into a hugely successful online platform.
The memo also indicated that Melissa Bell and Dylan Matthews, who were also involved in Wonkblog, will be leaving with Klein.
This post has been updated.