About one woman in 70 is at risk of developing ovarian cancer, which claims more than 4,200 lives a year.
However, for those with a faulty RAD15D gene, the risk is raised to one in 11.
The discovery was made by scientists at the Institute of Cancer Research, which is connected to The Royal Marsden hospital in London.
Professor Nazneen Rahman, head of genetics and epidemiology, said: "At this level of risk, women may wish to consider having their ovaries removed after having children, to prevent ovarian cancer occurring."
At the moment the discovery, published in the journal Nature Genetics, is limited to the knowledge that faulty copies of this gene raise ovarian cancer risk.
But Prof Rahman said: "There is also real hope on the horizon that drugs specifically targeted to the gene will be available."
The study was based on comparing the DNA of women from 911 families with ovarian and breast cancer, to that from 1,060 people in the general population.
Cancer Research UK, which helped fund the study, described it as "the most significant ovarian cancer gene discovery for more than a decade".
Prof Nic Jones, the charity's chief scientist, said: "It’s incredibly exciting to discover this high risk gene for ovarian cancer.
"It’s further evidence that a range of different high risk genes are causing the development of breast and ovarian cancer and we hope there are more waiting to be discovered in different cancers.
"We believe the results of this research will help inform personalised treatment approaches and give doctors better information about risks of cancer to tell patients."
About 10 per cent of the 6,500 new cases of ovarian cancer every year are estimated to be in those with "a strong family history" of the disease, said Annwen Jones, chief executive of the charity Target Ovarian Cancer.
She said: "This new information, in the future, could help more women with a family history understand their personal risk of developing this disease."
Survival rates for ovarian cancer remain poor compared to other types. While 92 per cent of breast cancer patients now survive for at least five year from diagnosis, for ovarian cancer only about four in 10 do.