The world's last surviving male northern white rhino has died after months of ill health, his carers said.
Sudan, 45, lived at the Ol Pejeta Conservancy in Kenya. He was put to sleep on Monday after age-related complications worsened significantly.
His death leaves only two females - his daughter and granddaughter - of the subspecies alive in the world.
Hope for preserving the northern white rhino now lies in developing in vitro fertilisation (IVF) techniques.
Rhinoceroses - of which there are five species - are the second-largest land mammal after elephants. The white rhinoceros consists of two sub-species: the southern white rhino, with an estimated 20,000 living in the wild, and the much rarer and critically endangered northern white rhino.
Sudan, who was the equivalent of 90 in human years, was the last surviving male of the rarer variety, after the natural death of a second male in late 2014.
The subspecies' population in Uganda, Central African Republic, Sudan and Chad was largely wiped out during the poaching crisis of the 1970s and 1980s. Poaching was fuelled by demand for rhino horn for use in traditional Chinese medicine in Asia, and for dagger handles in Yemen.
The last few dozen wild northern white rhinos in the Democratic Republic of Congo had been killed in fighting by the early 2000s.
By 2008, the northern white rhino was considered extinct in the wild, according to the World Wildlife Fund.
The elderly rhino was being treated for degenerative changes in his muscles and bones, combined with extensive skin wounds.
Unable to stand up and suffering a great deal in his last 24 hours, Sudan was put down by veterinarians at the Ol Pejeta Conservancy, according to an official tweet.
"Sudan was the last northern white rhino that was born in the wild," said Jan Stejskal of Dvur Kralove Zoo in the Czech Republic, where Sudan lived until 2009.
"His death is a cruel symbol of human disregard for nature and it saddened everyone who knew him," Mr Stejskal said, according to the AFP news agency.
In 2009, the four remaining northern white rhinos, two males and two females, were transferred from the Czech zoo to Ol Pejeta in Kenya.
The hope was that the new environment, reflecting their native habitat, would encourage breeding.
However, there were no successful pregnancies and Sudan was retired from his role as a potential mate four years ago.
An account was created for him on the dating app Tinder last year, not to find love, but to help fund the development of IVF for rhinos.
The move won him fans across the world - fans who will now be mourning his death and the northern white rhino's proximity to extinction.
Sudan's genetic material was collected on Monday, conservationists said, to support future attempts to preserve the subspecies.
The stored semen, and eggs from the remaining younger females, still gives conservationists hope that Najin and Fatu will be able to have their own calves one day.