Manwaring succeeds Richard Brewster who announced his resignation in July after seven years at the helm of the disability charity.
Manwaring said: "The time is now right for Scope to reinforce its role as the key organisation striving for disabled people to achieve equality.
I hope that we will quickly show how best to achieve equality through diversity, and show how by working with disabled people we can create tangible positive changes in their everyday lives."
Brewster, who is moving to the US, is to leave in February. Manwaring will join in January to allow for a hand-over period.