Researchers say the world's last male northern white rhinoceros, Sudan, has died after "age-related complications".
A statement from the Ol Pejeta Conservancy in Kenya says the 45-year-old rhino was euthanised on Monday after his condition "worsened significantly" and he was no longer able to stand.
The rhino had been part of an ambitious effort to save the subspecies from extinction with the help of the two surviving females.
"He was a great ambassador for his species and will be remembered for the work he did to raise awareness globally of the plight facing not only rhinos, but also the many thousands of other species facing extinction as a result of unsustainable human activity," said the conservancy's CEO, Richard Vigne.
Sudan was something of a celebrity, attracting thousands of visitors.