Ron Weber, an English professor in Ottawa, Ontario, lived for 40 years with a degenerative spinal disease, in what he called the “black hole” of chronic pain.

On a July day in 2022, Mr. Weber, 64, ate a last bowl of vegetable soup made by his wife, Lori, and, with the help of a palliative care doctor, died in his bedroom overlooking a lake.

Aron Wade, a successful 54-year-old stage and television actor in Belgium, decided he could no longer tolerate life with the depression that haunted him for three decades.

Last year, after a panel of medical experts found he had “unbearable mental suffering,” a doctor came to his home and gave him medicine to stop his heart, with his partner and two best friends at his side.

Argemiro Ariza was in his early 80s when he began to lose function in his limbs, no longer able to care for his wife, who had dementia, in their home in Bogotá.

Doctors diagnosed A.L.S., and he told his daughter Olga that he wanted to die while he still had dignity. His children threw him a party with a mariachi band and lifted him from his wheelchair to dance. A few days later, he admitted himself to a hospital, and a doctor administered a drug that ended his life.

Until recently, each of these deaths would have been considered a murder. But a monumental change is underway around the world. From liberal European countries to conservative Latin American ones, a new way of thinking about death is starting to take hold.

Stephanie Nolen is exploring access, attitudes and approaches to medically assisted death around the world.

Over the past five years, the practice of allowing a physician to help severely ill patients end their lives with medication has been legalized in nine countries on three continents. Courts or legislatures, or both, are considering legalization in a half-dozen more, including South Korea and South Africa, as well as eight of the 31 American states where it remains prohibited.

It is a last frontier in the expansion of individual autonomy. More people are seeking to define the terms of their deaths in the same way they have other aspects of their lives, such as marriage and childbearing. This is true even in Latin America, where conservative institutions such as the Roman Catholic church are still powerful.