Nearly 30 countries have jointly pledged $4.1 billion (£2.9bn) to protect the environment and human wellbeing.
The support for the Global Environment Facility (GEF), for a further four years, will help developing countries tackle environmental degradation.
Funding will be used to protect the marine environment, including from plastic waste pollution.
With the seventh round of support, the GEF is planning to protect around 600 million hectares of land and marine habitats – equivalent to 24 times the size of the UK – and reduce greenhouse gas emissions by 1,600 million metric tonnes.
The UK has committed up to £250 million over the next four years.
International Development Secretary Penny Mordaunt said: “The UK’s long-running partnership with the Global Environment Facility has already achieved great change – cutting greenhouse gas emissions and protecting land – and now we’re working with out international partners to do more so that together we can clean our oceans of plastic waste and fight illegal wildlife trade.
“This will help developing nations but as we are all affected by the environment, it is a win for us in the UK too.”