Dr Macneil, who is from Canberra, has accepted her appointment as 11th Bishop of the Anglican Diocese of Grafton. She will be consecrated and installed early next year.
Other women have been consecrated as assistant bishops within Australian Anglican dioceses and, overseas, women have been made diocesan bishops but this is a national first for Australia.
Dr Macneil said she was "surprised, overwhelmed, humbled" to be the first Australian women elected a diocesan bishop.
"I am awed by the confidence placed in me by the [Grafton Diocese] appointment board and by their willingness to be trailblazers," she said.
Dr Macneil is a former Dean of Adelaide and archdeacon in the Diocese of Canberra-Goulburn. She is presently Senior Associate Priest at Holy Covenant in Jamison, ACT.
Start of Royal Commission hearings
The Diocese of Grafton is facing a number of significant challenges, not least the hearings that begin this week before the Royal Commission into Institutional Responses to Child Sexual Abuse in relation to historical cases from the North Coast Children's Home.
For her part, Dr Macneil, said she was "struck by the faithfulness, openness and resilience of the people of the diocese, lay and ordained" in facing these issues.
"In recent times the Diocese of Grafton has faced financial difficulties and is now appearing before the Royal Commission... There is a determination among the people of the diocese to understand what has gone wrong in the past, to ensure that it does not happen again and to embrace the future with hope, trusting in God."
Dr Macneil said that during the discernment period she became increasingly aware that had some key skills the Diocese needed at this time.
"There seems to be a good match between my gifts, skills and experience and the particular mix of qualities the diocese was looking for at this stage of its life. They are keen to have a bishop with a heart for mission in the 21st century, a respect for the diversity of Anglicanism and with administrative experience, all of which are part of my story," she said.
"I am excited at the prospect of being part of this rebuilding and refocussing and humbled by the confidence the selection board has placed in me. I am particularly looking forward to getting to know the people of this diverse and beautiful diocese," she said.
Dr Macneil was selected from a number of candidates by a Nomination Board appointed by Diocesan Synod. While details of the appointment process are confidential it is understood Dr Macneil's selection was unanimous.
Twenty years since first ordination of a woman as priest
Her election comes almost 20 years to the day since the first ordination of a woman in Grafton diocese which embraces the North Coast of NSW, extending from Port Macquarie to the Queensland border.
Her election will cause considerable excitement in church circles, not only among Australian Anglicans but in mainline churches around the world.
It will be interpreted by many as an overt sign of an increasing acceptance of women in leadership roles within the church.
Her consecration in Christ Church Cathedral, Grafton, early in 2014 is expected to draw a large number of people who have been prominent in the advocacy of women in leadership within the Anglican Church during the last 3o years.
Colleagues describe Dr Macneil as having a servant heart, being prayerful, possessing insight and humour and delighting in diversity within the church.
She is a life time Christian in the Anglican tradition and, before ordination, worked in Australia and abroad with the Commonwealth Departments of Foreign Affairs and Trade.
Bishop-elect Macneil is a member of the Standing Committee and of the Anglican Consultative Council