The sad news was announced by Blackpool Zoo on Wednesday afternoon (April 13).
Darwin was thought to be around 105 years old, but his exact age was unknown as there were no detailed records of his history.
He had been receiving specialist treatment for a leg problem for which there was no cure, but his condition had sadly deteriorated.
Despite the efforts of his keepers and veterinary team, and consulting with worldwide reptile veterinarians, the difficult decision was made to put him to sleep.
“Staff and keepers are extremely saddened at his passing and are being comforted by the kind messages of condolence we are receiving,” a spokesman for Blackpool Zoo said.
“Darwin arrived before the zoo opened in 1972 and became an iconic animal due to his vast size.
“He was a wonderful link for so many people to the fascination of reptiles and he has really inspired the next generation of conservationists.”
Aldabra tortoises are one of the largest species of tortoise in the world originating from the islands of Aldabra Atoll, Seychelles, and they are the longest living animal on the planet.