He's been consecrated by the Christian Episcopal Church, a breakaway group from the US Episcopal Church - which is part of the Anglican Communion.
Ashenden will work alongside Anglicans in the UK and further afield who are unhappy at the perceived move away from orthodox Christianity
The appointment is similar to that of Andy Lines who was made a missionary bishop to the UK and Europe by GAFCON, a worldwide group of conservative Anglicans.
Rev Jonathan Pryke from Jesmond Parish church was also consecrated as a "bishop in the Church of God" by the Reformed Evangelical Anglican Church of South Africa, another breakaway group.
Bishop Ashenden will work alongside a number of groups, who have come together to form the Unity Forum, looking to stand for traditional teaching on sexuality and other issues.
Rt Rev John Fenwick, convenor of the Unity Forum, said: "Gavin's stand for orthodoxy has been an encouragement to Anglicans in the UK and beyond.
"We look forward to working closely with him as we face the challenges that lie ahead."
In a statement welcoming the appointment of Bishop Ashenden, Most Rev Theofore Casimes of the Christian Episcopal Church, said: "As the Church of England is in the process of abandoning Christian teaching on culture, sexuality, marriage and the uniqueness of Christian revelation, the Bishops of the Christian Episcopal Church believed that it was their responsibility to offer a renewed episcopal oversight and encouragement to those Anglicans in the UK and Europe who had become distressed and disillusioned by the changes of direction and the adoption of secular values by the Church of England."
Dr Ashenden was ordained as an Anglican priest in Southwark Cathedral in 1980. He worked in parishes in South London for ten years before becoming a University Chaplain and a lecturer in the Psychology of Religion for 23 years.
He was a member of the General Synod for 20 years and in 2008 he was made a Chaplain to the Queen.
In 2017 he resigned as Chaplain to the Queen so that he could speak out more freely in the wake of the Quranic readings in Glasgow Cathedral which denied the divinity of Christ.