The West Australian government has officially opened the $2 billion Fiona Stanley Hospital in Perth.

West Australian health minister Kim Hames has apologised for the delay in opening the state's new $2 billion hospital, saying the original completion date was never possible.

Fiona Stanley Hospital in Murdoch was expected to open in April, but instead, the first stage started on Friday and the facility will not be fully operational until next year.

Dr Hames said he had not realised the previous Labor government had planned for the hospital to be ready just three months after construction was due to be completed.

"It was never a practical opening date," he said on Friday.

"I take responsibility for not picking earlier that I should have delayed it at the start.

"But the reality is we had to have it safe for patients, we had to have people well trained (and) we had to fit it out."

About 120 patients from Shenton Park Campus will move to the new rehabilitation facilities at FSH on Saturday.

Selected general surgical, orthopaedic, anaesthetic and obstetric services will be introduced from November, as well as clinical services in the main hospital, while the emergency department is expected to open in February.

WA Labor, which started the project when it was in government, has since been critical of the state government's handling of the project but still welcomed the opening of the hospital, which will have 783 beds when fully operational.

FSH was initially planned as WA's first paperless hospital, with mobile computers and tablets used to record patient information.

But problems implementing the system caused delays and the plan was scrapped.

A contract with Serco, the hospital's private operator of non-clinical services, also had to be renegotiated.

Australian epidemiologist and former Australian of the Year Fiona Stanley said it was an honour to have the hospital named after her, but it was hard to be told she was "the biggest thing in the southern hemisphere", "blown out" and "not on time".

Dr Stanley said she envisaged FSH would become a renowned world centre in medical research and patient care that attracts the top health professionals from around the globe.