The facility at Werribee Open Range Zoo includes two new operating theatres, two large wards, a neonatal room, pharmacy facilities and twelve recovery pens.

Staff will soon begin working in the hospital and it will start taking patients in the coming months.

The $2.55 million project was funded almost entirely by donations from the public following the Black Summer bushfire crisis in 2019 and 2020.

The RSPCA contributed $1.5 million towards infrastructure and equipment while philanthropic donations to Zoos Victoria's Emergency Wildlife Fund financed the majority of the rest of the project.

On average one injured koala is taken to Zoos Victoria facilities every three days and it can take up to a year before they are well enough to be released back into the wild.

"I think our vets are still pinching themselves," CEO Dr Jenny Gray said at the opening on Friday.

"What the koala Ward allows us to do is treat wildlife without mixing it with the animals that live at the zoo."

"So that gives us another level of biosecurity by having two facilities and allows us to have that surge capacity in the event that we would required it."

There are approximately 450,000 koalas living in the wild around Victoria, according to a 2020 study by scientists at the Arthur Rylah Institute for Environmental Research.

RSPCA CEO Dr Liz Walker said the new facility will ensure more animals get medical care in the event of another large natural disaster.

"The support of the community in providing enormous contributions and donations to making this happen is is just incredible", she said.

"We have future proofed our ability to care for wildlife."

The new facility is designed to primarily care for koalas but is also equipped to care for native birds, reptiles and other mammals.

Minister for the Environment and Climate Change Lily D'Ambrosio said it will allow even more injured animals to return to their natural habitat.

"It's a new ward for koalas that are injured either through climate change or bushfires or indeed injured in other ways," she said on Friday.

"The objective is not only for those koalas to continue to stay alive but to hopefully be able to thrive and prosper."

Treasurer and Member for Werribee Tim Pallas said the focus of zoos around the state is changing to include a greater emphasis on preservation and research.

"This facility will be a reminder that we do have an obligation, not only to other creatures, but to our environment and future generations that will be the beneficiaries of that legacy."

Australian Associated Press