Ritchie, who has already stood down from the Wembley Stadium board, will also relinquish his non-executive director role with the Football League before taking up his position at Twickenham.
Ritchie's brief will be to lead the RFU out of arguably the most turbulent year of its history and towards England's golden opportunity of hosting the 2015 Rugby World Cup.
The RFU spent 2011 in a state of managerial turmoil. The fall-out from John Steele's departure as chief executive was poisonous, damaging and expensive to the governing body.
One of his first jobs will be to oversee the appointment of the new permanent England coach.
"I am very much looking forward to meeting and working with new colleagues and partners at the RFU," Ritchie said.
"There is much to be positive about, seeing a new generation of players emerge in the RBS 6 Nations and seizing the unique chance to grow the game when hosting the Rugby World Cup in 2015 is very exciting.
"Joining the RFU as CEO was an irresistible opportunity. It was a very difficult decision to leave the All England Lawn Tennis and Croquet Club but I know they have a fantastic team and I wish them continued success for the future."
Ritchie was identified as the "standout candidate" from the RFU's shortlist, with the interview panel impressed by his experience in business, leadership and sports administration.
He was appointed to the Football League board in April 2004 as the first independent non-executive director of a domestic football governing body. Ritchie joined the Wembley Stadium board in July 2008.
"When it created this role, the Football League was looking for somebody to bring greater levels of independence, continuity and insight to its decision-making process. Ian has delivered in every way. On behalf of our clubs, I would like to wish him every success in his new job at the RFU," said Football League chairman Greg Clarke.
Ritchie has previously held chief executive posts with Channel Five and Middle East Broadcasting. He was vice president of global business at the Associated Press before taking over at Wimbledon in 2005.
"We are very pleased that Ian can join so soon. It is well acknowledged that he has a fantastic reputation and the RFU will quickly benefit," said RFU chairman Paul Murphy.
"His appointment has been exceptionally well received around the game and I know the staff cannot wait to work with him."
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