Currently the HCA's director for the North East, Ritchie will take up her new role on 1 November on an interim basis and will remain in post until a permanent appointment is made next year.
Ritchie has been the HCA's director for the North East since the agency was launched in December 2008. She replaces Sir Bob Kerslake, who moves to become permanent secretary at DCLG.
Ritchie said: "I am excited to be leading the agency at this crucial time. The job ahead will be extremely challenging as we reshape the HCA to support the government's commitment to localism and drive out the best possible value for public money.
The HCA has an important long-term role and a strong offer to make to local authorities to help deliver their ambitions."
HCA chairman Robert Napier said: "I and the HCA board are delighted that Pat Ritchie will be our new chief executive.
"We were fortunate to be able to recruit from an extremely talented pool of existing directors and in doing so we considered a number of strong applicants.
"She has a strong track record of achievement, both in the North East and in leading change at a national level, as well as the respect of staff and the sector as a whole. She has the talent and skills to drive the agency forward."