Answering a 1958 advertisement in the medical journal the Lancet, two Australian doctors moved to Addis Ababa, Ethiopia’s capital, to work as obstetricians and gynecologists. They were married, had a 6-year-old son and figured they would stay three years.

Instead, they remained for the rest of their lives, devoting themselves to improving childbirth outcomes for thousands of mothers — and especially for young women and teenage girls whose debilitating deliveries left them injured, incontinent and ostracized from their communities, suffering from a condition known as obstetric fistula.

Caused by long, obstructed deliveries in which babies get stuck in the birth canal, the injury was common around the world before the introduction of modern Caesarean deliveries. (Until the late 19th century, a fistula hospital stood at the site of the Waldorf Astoria hotel in Manhattan.)

Catherine Hamlin and her husband had never treated the injury in Australia. But after turning to the medical literature as well as peers overseas, the Hamlins perfected surgical techniques that revolutionized fistula treatment for women in Ethiopia. Amid a communist revolution and civil war, they established an Addis Ababa hospital entirely devoted to fistula procedures, followed by five regional hospitals, a midwives’ college and a rehabilitation center for fistula patients.

Dr. Hamlin, who was 96 when she died March 18 at her home in Addis Ababa, continued her work long after her husband Reginald’s death in 1993. Known in Ethiopia as Emaye, or Mother, she helped galvanize a global health movement, appearing on “The Oprah Winfrey Show,” testifying before Congress and sparking the 2003 launch of the Campaign to End Fistula, a project of the U.N. Population Fund. In 2014, New York Times columnist Nicholas Kristof called her “a 21st-century Mother Teresa.”

“There’s no question that she was a role model, a leader, for all people doing maternal health,” said Lynn Freedman, a population and family health expert at Columbia University’s Mailman School of Public Health. “She treated women who had fistula with a kind of compassion, and a respect for the wholeness of their lives as human beings, that was extraordinary.”

Dr. Hamlin’s death was announced by the Australian charity Catherine Hamlin Fistula Foundation, which did not cite a cause. It said the health-care network she co-founded, Hamlin Fistula Ethiopia, had treated more than 60,000 fistula patients.

While worldwide data is limited, the Campaign to End Fistula estimates that 50,000 to 100,000 new fistula cases occur each year, with about 2 million women untreated across the globe. Many live in patches of Asia and sub-Saharan Africa where obstetric care is limited. Almost all cases result in a stillbirth, and some patients struggle with nerve damage in addition to debilitating social treatment.

Dr. Hamlin performed surgeries on young mothers smelling of urine and feces, who were sometimes forced from their homes and exiled to the outskirts of their villages. Her first fistula patient was a 17-year-old who arrived in urine-stained clothes, the result of a harrowing five-day delivery that left a hole between her bladder and birth canal. Later patients included a woman who had to beg for six years before she could afford a bus fare to the Hamlins’ chief care center, Addis Ababa Fistula Hospital.

Through the years, Dr. Hamlin developed a three-pronged approach to fistula: training rural midwives to prevent the injury altogether; providing high-quality treatment for patients; and aiding women in their reentry to society, including through literacy classes. That approach formed a blueprint for the Campaign to End Fistula, said Kate Ramsey, the group’s former global coordinator.

“Her legacy in Ethiopia is not that she put herself out there as a hero,” Ramsey said, “but that she trained and supported and really encouraged all these Ethiopian surgeons who are now considered some of the world’s foremost experts in fistula surgery.”

Through her focus on the procedure, Dr. Hamlin refined surgical techniques as well as pre- and postoperative care for fistula patients, said surgeon Ambereen Sleemi, executive director of International Medical Response. The nonprofit organization performs fistula surgery and trains doctors in Liberia, Haiti and Malawi. “Her hospital is the gold standard for how we care for these women now,” Sleemi said.

Dr. Hamlin sometimes described herself as a Christian missionary and called the women who flocked to her hospital “fistula pilgrims.” “These are the women most to be pitied in the world,” she told Kristof in 2003. “They’re alone in the world, ashamed of their injuries. For lepers, or AIDS victims, there are organizations that help. But nobody knows about these women or helps them.”

After receiving treatment from Dr. Hamlin, many joined her medical crusade against fistula. One patient was sold at age 13 to be the wife of a 60-year-old man, then became pregnant, delivered a child by herself in the bush and suffered a severe fistula, forcing her to crawl for help, Kristof wrote in 2014. She later joined Dr. Hamlin’s hospital as a nurse’s aide.

Another patient, an illiterate woman named Mamitu Gashe, was treated at the hospital and stayed on to learn how to perform fistula repairs. “When distinguished professors of obstetrics from around the world come to this hospital for training in fistula repair,” Kristof wrote, “their teacher has often been Mamitu.”

Dr. Hamlin’s six-decade stay in Ethiopia was a stark departure from her wealthy upbringing in the suburbs of Sydney, where she was born Elinor Catherine Nicholson on Jan. 24, 1924. Her father was an engineer who made a fortune from the elevator business, acquiring a yacht and ponies for his six children, according to a report in the New Zealand Herald.

Catherine studied at Frensham boarding school in Mittagong before graduating from the University of Sydney’s medical school in 1946. She completed her residency in obstetrics at Crown Street Women’s Hospital in Sydney, where she met hospital superintendent Reginald “Reg” Hamlin, a New Zealander who was 15 years her senior.

They married in 1950 and worked at hospitals in London and Hong King before settling in Addis Ababa, where they were initially based at the Princess Tsehai Memorial Hospital. Within their first three years, they had treated 300 fistula patients.

The couple treated thousands more after founding Addis Ababa Fistula Hospital in the mid-1970s, and remained in the country even as it devolved into civil war, with gunfire occasionally bursting through their living room.

“We couldn’t have left,” Dr. Hamlin told the World Health Organization in 2013. “Who would run the hospital? Who would look after these women? They kept ringing us to say, ‘The last plane out is tomorrow night, are you ready?’ My husband and I said, ‘No, we are not leaving, we are going to stay here.’ ”

Dr. Hamlin called her husband “the driving force” behind their health-care organization. She became its public face after his death and received awards, including the Companion of the Order of Australia, although she never seemed entirely comfortable with the attention.

“I don’t think I am anything like what people think I am,” she told Australia’s Canberra Times newspaper in 2001. “I’m not a great surgeon. I fix holes in women plumber-like. A lot of gynecologists could do this.”

Survivors include her son, Richard Hamlin; a sister; two brothers; four grandchildren; and two great-grandchildren. At Dr. Hamlin’s 90th birthday, her son also recognized her legions of former patients as extended family members, declaring, “Catherine has one son and 35,000 daughters.”

Dr. Hamlin, in turn, urged those in attendance to continue her fight against fistula in the years to come. “We have to eradicate Ethiopia of this awful thing that’s happening to women: suffering, untold suffering, in the countryside,” she said at the birthday celebration. “I leave this with you to do in the future, to carry on.”