Satao II, a 50-year-old so-called "giant tusker, was found dead on Monday and was believed to have been shot with a poisoned arrow in Kenya.
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The elephant, named after another giant killed in 2014, was beloved by visitors to Tsavo national park.
There are now fewer than 30 African "big tuskers" - adult bulls with ivory large enough to brush the ground - in the world.
"I am pretty gutted really," Richard Moller, head of the Tsavo Trust, said.
"This particular elephant was one that was very approachable, one of those easy old boys to find. Many are the others are much more difficult to see.
"He has been through lots of droughts and probably other attempts at poaching."
Satao II was one of Africa's oldest and biggest elephants
A team from the park and Kenyan Wildlife Service recovered the animal's enormous ivory tusks intact, before poachers could claim them, the park said.
His carcass was discovered in January during routine aerial surveillance of the 25,000 sq km national park, but was only announced Monday.
After the discovery, the park's teams tracked an "elephant poaching gang" deep into the park, and two poachers were arrested.
Among the items found with the poachers were three bows and 12 poisoned arrows, as well as an AK47 rifle, the park said.
"Although this is a very sad loss in every way, we can take some positive from this in that Satao's carcass was indeed found with the ivory intact, and recovered before it could fall into the wrong hands and further fuel the illegal ivory market," the Tsavo Trust said.
"More importantly, this poaching gang has been broken for ever."