Klein, who is expected to start his new role before the end of the year, is currently the BBC's head of independent commissioning, knowledge.
In this role, which he has held for almost a year, he oversees all commissioning from independent production companies across features, arts, music, religion, specialist factual and documentaries. Recent commissions include 'Stephen Fry: The Secret Life of the Manic Depressive' and 'Wonderland'.
He joined the BBC in 1996 as a series producer and moved into commissioning to become a commissioning executive.
From there, he became a senior commissioning executive and then the commissioning editor for documentaries in March 2005.
Jana Bennett, director of BBC Vision, said: "Richard is a bold thinker, capable of bringing a strong singular vision to the channel.
"He is able to reach out to the creative community, commissioning thought-provoking programmes, with an individuality of voice, wit and charm.
"Richard has been part of BBC Four's success from the very beginning and will ensure that the channel continues to cover a broad range of specialist subjects while taking it on to the next stage."
Klein takes over from Hadlow, who took up the position of controller of BBC Two earlier this month.
Klein said: "I'm thrilled and excited at the prospect of leading BBC Four, a channel with an extraordinary range of voices and a unique outlook on the world.
"It's daunting to be following in the footsteps of Janice, who has done a great job, but a rare privilege to have the opportunity to run such an intelligent, challenging and stimulating channel."
.jpg)
.jpg)