Mark Shand - the brother of the Duchess of Cornwall - was the chairman of Elephant Family, which aims to save the endangered Asian elephant from extinction in the wild.
In a statement, the charity said it had "lost the head of our family".
The statement on the charity's website reads: "Today we have lost the head of our family. Mark Shand was a true force for conservation.
"He was both a legend and inspiration and above all our great friend. We ask at this time that people’s thoughts are with his loved ones. We will miss him always."