By Deutsche Presse Agentur
After being greeted by Vietnamese Prime Minister Nguyen Xuan, William is expected to meet local Vietnamese business, environmental and cultural leaders.
On Thursday, he will attend the third International Wildlife Trade conference in Vietnam's capital, organised by the British Embassy in Vietnam and the Vietnamese Administration of Forestry.
Other participants include high-ranking delegates from more than 50 countries and 10 international organisations.
The aim of the conference is to "help eradicate the illegal wildlife trade and better protect wild species from the threat of extinction "by bringing together a wide range of global figures, according to the event's official site.
Vietnam is one of the biggest consumers of elephant ivory and rhino horn worldwide.
Some locals believe rhino horn has important medicinal and aphrodisiac properties, and it is seen as a status symbol.
Ivory, of which at least 40 tonnes have been seized since 2011, is frequently transported to the Chinese market from Africa by way of Vietnam.