Three-time world champion Tweddle is set to retire after completing her set of major championship medals at the London 2012 Olympics but Reddin, who competed at the 1984 Games in Los Angeles, is already guiding through many of her successors.
And that makes her a natural appointment, according to British Gymnastics performance director Tim Jones.
"Amanda's knowledge of the system that had been put in place to put our British programme in the top tier of the world is second to none," he said.
"She also has a clear vision of the direction we now need to move forward in order to challenge for Olympic medals on a regular basis."
Reddin has guided City of Liverpool to multiple British titles and will take up her new role at the start of next month, succeeding Adrian Stan, who is now responsible for high performance coach development.
"It is a great honour to be appointed as head national coach and I'm excited to take on the challenge of continuing the great legacy left by Adrian Stan," said Reddin.
"I look forward to building relationships with coaches and gymnasts as we look ahead to European and World Championships in 2013."