The man, who was given the pseudonym Robert Masson in court, said he had donated his sperm with the understanding that he would be involved with the child’s life.
In addition, the court found that Mr Masson’s name appeared on the child’s birth certificate as her father and he had “an ongoing role in her financial support, health, education and general welfare”.
The dispute emerged when the mother and her same-sex partner decided to move to New Zealand and Mr Masson challenged their decision in Australia’s Family Court.
Although the family court ruled in favour of Mr Masson and ordered the mother and her partner to remain in Australia so the child could spend regular time with him, an appeal ruled in favour of the two women.
The case came down to a judgement on whether New South Wales (NSW) law should apply instead of commonwealth law.
In NSW law, a sperm donor is not a father of a child.
However, the high court decided it was wrong to characterise the father as simply a “sperm donor” because he had given his sperm under the belief that he would be the child’s father and had supported and cared for her as a parent.
Mr Masson was also said to have treated his child’s younger sister as his daughter, despite her not being his biological child, and both children called him “daddy”.
The ruling could have major implications for parents who use a sperm donor who is known to them and who allow the donor to be involved in their child’s life.
Stephen Page, a family lawyer, told ABC Australia the decision could also affect sperm donors who do not believe they have parental obligations.
"I can assure you that there are men who thought they were sperm donors and had no obligation to the child … and have now discovered that potentially they have the full gamut of responsibility, including potentially child support and inheritance," he said.
The high court ruling did not define at what point a person would transition from being classed as a sperm donor to a legal parent.
However, donors who remain anonymous would not be classed as parents under the ruling.
Australia’s attorney general, Christian Porter, previously backed Mr Masson in the case and welcomed the ruling.
“Parenthood requires a court to consider all of the broad range of circumstances that might exist in the individual practice,” he said.
“This was a pretty individual and unique set of facts and circumstances.”