The Hong Kong government has banned shark fin, bluefin tuna and black moss from the menu at official functions, hoping to "set a good example".
And officials have been ordered not to eat them if they are served up at non-government banquets.
Bureaus and departments will also be encouraging other organisations to adopt the ban.
"Since it is not possible to list all food items of concern exhaustively, the exclusion of these three items from official menus is a start and also serves as an example to raise public education and awareness about sustainability," a spokesman said.
He said eating shark fin, bluefin tuna and black moss - a type of bacteria that grows in hair-like strands - was widely frowned upon in Hong Kong and internationally.
The International Union for Conservation of Nature has listed 74 species of sharks as vulnerable, endangered or critically endangered, and says finning is inhumane.
Bluefin tuna is also endangered, with numbers having fallen by half over the past four decades.
Overharvesting of black moss - or fat choy in Cantonese, which sounds like "struck it rich" - has led to desertification in northern parts of China.
The government spokesman said internal guidelines issued by the Environment Bureau stipulated that officials should notify their hosts of the food ban in advance when they accepted banquet invitations.
"The government will keep in mind local and international trends on green living in line with a sustainability-conscious lifestyle and update the list of items from time to time," the spokesman said.
There had already been an unofficial ban on shark fin at government banquets but yesterday's pledge was the first official statement.
WWF welcomed the government's move, saying it would help get the message of conservation across.
But it said it hoped the government would also collect statistics on the shark fin trade to show what species were being sold so consumers would know exactly what they were buying or eating.
The WWF also hoped more organisations would follow the government's example.
It said 154 companies and organisations had joined its "Say No to Shark Fin" campaign and 115 restaurants had pledged it would not appear on their menus.