Gellinudd Recovery Centre, in Pontardawe, Swansea, is not-for-profit and developed by charity Hafal.
Part-funded by Big Lottery and the Welsh Government, staff say it will take a more rounded and fulsome approach to treatment.
This includes people's physical health and social lives as well.
The centre's design is based on the ideas and shared experiences of adults with mental health illnesses such as depression and schizophrenia.
It has a large living space with an interactive touch screen TV, a kitchen, a crafts room and 16 bedrooms.
There is also a treatment room and a play room for guests who have children.
Director Alison Guyatt said it would be "a world-class facility and the only service of its kind in Wales and the UK, which we hope will set new standards of best practice".
People will be asked to set out recovery goals in different areas of their lives as part of their treatment plan.
Sian Shortman from Maesteg, Bridgend county, struggled with serious depression from a very young age and self-harmed as a teenager.
She said: "If there had been somewhere like this around when I was younger it would have been a lot better and I don't think I would be where I am today with my mental health problems if I had somewhere like Gellinudd to go.
"It really means a lot to me that in future people will finally get the help they deserve."
The centre is close to beauty spots like the Gower Peninsula and Brecon Beacons, with trips forming part of the therapy.
Health Secretary Vaughan Gething will be at the opening and the Welsh Government has invested £500,000 in the scheme in the hope it will save the NHS an estimated £300,000 each year through the care it provides.
Gellinudd was developed with the NHS to ensure it meets clinical governance standards.
Hafal trustee Mair Elliot said: "It works because it is based on the experiences of hundreds of people who have been through mental illness and recovery."
A "UK first" £1.5m mental health centre which has been designed with the input of people who have experienced an illness will officially open later.