PA Sport 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.
"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'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 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.
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.
