Sienna Miller has spoken of the "fierce dedication" of local aid workers in providing disaster relief, and called on people to support humanitarian causes across the world.
Ms Miller was speaking at the launch of the First Responders campaign honouring the millions of unsung heroes around the world responding to global disasters every day.
The project, which is funded by the European Commission, aims to train and support communities in disaster prone areas as they are most often the fastest and most effective providers of relief when natural disasters strike.
Sienna Miller, an ambassador for the International Medical Corps, said it was crucial to "help people help themselves" in disaster zones across the world.
"My role is to raise awareness because ultimately we are all first responders and we have to support those on the frontlines," she said.
"We're here today, and throughout 2014, to celebrate the unsung heroes who respond to global disasters every day.
"We're asking people, and especially young people, across Europe to pledge their support."
The launch of First Responders in London today was also attended by the European Commissioner for International Co-operation and Crisis Response, Kristalina Georgieva.
Ms Georgieva said: "Helping people help themselves matters for all of us. We have to build up communities so they are able to identify their risks and help their children."
The commissioner said that the frequency of natural disasters and climate change meant all communities needed training in providing relief.
"We need a change of mindset to make each and all of us a first responder because climate change is happening in the UK as well as very poor countries," she said.
"People in communities are not stupid. If you live in Niger you know that droughts will come like never before."
She added: "My favourite story is from Bangladesh where floods always hit. So what have people done? They have switched from rearing chickens to ducks, because in floods chickens die and ducks swim."
Ms Georgieva also recalled when she was called upon to act as a first responder during an earthquake in Romania in 1976.