EBay has announced a worldwide ban on the sale of ivory products on its auction websites from next year.
An eBay spokesman said the move was the best way to help African and Asian elephants. The endangered animals are often hunted for their ivory tusks.
The ban comes as a conservation group prepares to release a report critical of the auction site.
The International Fund for Animal Welfare will say more than 4,000 ivory products have been listed on eBay.
Most sales of ivory products through eBay are done on the company's American website.
"In one instance, a user purchased a pair of elephant tusks off eBay for more than $21,000," the International Fund for Animal Welfare said.
EBay said it would still allow the sale of some antique items which contain a small amount of ivory, such as pianos.
Campaigning groups the Humane Society of the United States and Humane Society International welcomed the decision.
Teresa Telecky, policy director for Humane Society International, said eBay's decision was "commendable and should set an example for others".
Each year, an estimated 20,000 elephants are illegally killed in Africa and Asia for their ivory, fuelling a booming black-market industry.
Elephants are protected under the International Convention on the International Trade in Endangered Species (Cites).