She replaces Les Lawrence, lead member for Birmingham, who steps down after more than three years in the post.
He will now chair the LGA's safer communities board, which works closely with the children and young people board to help local authorities offer joined-up services for families.
Lawrence and Ritchie, who are both Conservative councillors, will formally take up their posts from September.
Ritchie said: "I am very excited about my appointment. It has been a very difficult time for children's services, so I really hope I can help lead members to make a positive contribution to the wellbeing of children and families. I shall also look forward to lobbying government to secure as much funding as possible for children's services."