The couple's Jolie-Pitt Foundation is contributing $1 million to the emergency medical operation responding to the disaster.
"It is incredibly horrible to see a catastrophe of this size hit a people who have been suffering from extreme poverty, violence and unrest for so many decades," says Angelina.
Brad adds: "We understand the first response is critical to serve the immediate needs of countless people who are now displaced from their homes, are suffering trauma, and most require urgent care."
The money will go to Doctors Without Borders/Médecins Sans Frontiéres. The organisation's three hospitals in the capital Port-au-Prince were badly damaged, forcing the staff to work in the open air.
Other stars urging support include Coldplay frontman Chris Martin. The singer asked people to give money to a Haiti appeal set up by Oxfam.
Chris visited Haiti with the charity a few years ago. At the time he found a country to be "of extreme poverty and brutal living conditions" with people in Port-au-Prince living in shacks.
The earthquake, he said, probably turned the city "into an unimaginable hell".
Many stars, including Haiti national Wyclef Jean, have taken to Twitter to ask fans to pledge their support. Ben Stiller tweeted that "people in Haiti need our help and attention right now".
P Diddy posted numerous messages giving advice on how to help and another saying: "My heart is so heavy today! Words can't explain! God Bless Haiti!". Similar messages have been appearing from the likes of Paris Hilton, Katy Perry and Lindsay Lohan.
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