The RFU has been without a permanent chief executive since ex-Northampton player and coach John Steele departed in June after just nine months in office.
"I believe English rugby has a very bright future, culminating in a home World Cup in 2015," said Ritchie, who will look to guide England to the defence of their RBS 6 Nations crown.
"I am determined to help rugby create a legacy from the tournament that will benefit the sport for generations.
"The opportunity to lead an organisation which I know has so many dedicated, talented people is one I relish.
"The RFU has great commercial partners and a very sound financial base, underpinning the development of rugby union at grassroots and elite level.
"The decision to leave the AELTC was a difficult one. I have been fortunate to work for a wonderful organisation and am extremely proud of what it has achieved over the past few years."
Following Steele's departure Martyn Thomas, the former RFU chairman, took over but stepped down from the role late last month while his replacement, acting CEO Stephen Brown, will revert to his role as chief financial officer when Ritchie takes up his post.
Ian Metcalfe, the RFU board member who led the search for a new chief executive, said: "There was an excellent shortlist and we are confident that we have the very best person for the role of CEO to take the RFU and the game in England to the next stage of its development.
"We could not have wished for a better candidate who is so highly respected across sport and the business sectors.
"Ian clearly demonstrated the required knowledge and capabilities across a broad range of areas."