Part of being a celebrity means using your voice, your recognition and your wealth to make a difference in the world. It's almost an unspoken rule. But for some stars the likes of Angelina Jolie and Bob Geldof, humanitarian work almost becomes another career.

Whether it's poverty, disease, women's rights or climate change, there's always a major star out there using their popularity to raise awareness and money for it. Here are just a few of the world's most devoted celebrity humanitarians:

Angelina JolieAngelina Jolie has visited some of the bleakest countries in the world

Angelina Jolie: This Academy Award winner has visited more than 40 counties around the world doing field work for refugee aid in war-torn countries, wildlife conservation, education, orphans (adopting three children from poverty) and the protection of women's rights in conflict zones particularly in regards to sexual violence. She was a UNHCR Goodwill Ambassador for eleven years before being promoted to Special Envoy to High Commissioner António Guterres in 2012, and she was named Honorary Dame Commander of the Order of St Michael and St George by Queen Elizabeth II. She is currently a visiting professor at the London School of Economics where she is to teach a masters course at the Centre on Women, Peace and Security which she opened in 2015.

Ben AffleckBen Affleck helped co-founder the Eastern Congo Initiative

Ben Affleck: When a star's personal life hits headlines, it's easy to forget just how much they've given to the world. But Ben Affleck has done so much with the Eastern Congo Initiative; a campaign that helps to provide training and supplies to farmers in the African region in a bid to increase sustainable wealth among workers there. But his philanthropic efforts don't end there. He has supported charities such as the A-T Children's Project helping kids with ataxia-telangiectasia, Paralyzed Veterans of America and other war organisations including Operation Gratitude, cancer charity The Jimmy Fund and Feeding America's Entertainment Council.

Emma WatsonA UN Women Goodwill Ambassador, Emma Watson is a feminist role model

Emma Watson: After making a career out of playing a strong female role model in the 'Harry Potter' series, Emma decided to embrace her feelings on gender equality by launching her HeForShe campaign as part of her role as UN Women Goodwill Ambassador. Her work on women's rights have taken her around the world, and she further aims to educate women and men on the concept of feminism with her Goodreads book club, Our Shared Shelf.

Leonardo DiCaprioClimate change is Leonardo DiCaprio's biggest concern

Leonardo DiCaprio: 'The Revenant' star has always been a huge patron of environmental issues, establishing the Leonardo DiCaprio Foundation in 1998 as an official platform to tackle issues like global warming and renewable energy. An appointed UN representative on climate change, he's raised millions for green causes and has had direct discussions with such figures as President Bill Clinton, President Barack Obama and Pope Francis regarding such concerns. He has also been involved in several film projects including 'Before The Flood', 'Cowspiracy' and 'The 11th Hour'.

Charlize TheronCharlize Theron helps fight AIDS in Africa

Charlize Theron: A UN Messenger of Peace, Charlize Theron established her Africa Outreach Project in 2007, helping to protect vulnerable children in her home continent - primarily South Africa - from the toll of HIV and AIDS. As part of that project, she launch a shoe line with TOMS Shoes, 10,000 pairs of which were donated to poor children and a percentage of the proceeds from sales went to the Project. She has also stood up for women's rights, PETA and same-sex marriage.

More: Angelina Jolie does her first London School of Economics lecture

Bob GeldofWho can forget Bob Geldof's Live Aid?

Sir Bob Geldof: There's perhaps never been a celebrity-led humanitarian cause as widely populated as Band Aid. It was a movement aimed to help ease the famine in Ethiopia and spawned one of the best-selling charity singles of all time 'Do They Know It's Christmas?', while yet more money was raised with the corresponding Live Aid concert. He helped set up the Commission for Africa with the UK government in a bid to reduce debt repayments and increase aid to the poverty-stricken nations. 

BonoFew have raised more money for charity than Bono

Bono: Another Irish hero, the U2 frontman was another frontrunner in Geldof's Band Aid and Live Aid projects and joined him as part of the ONE campaign. He has also done a lot of work in regards to raising awareness of the AIDS pandemic, and co-established the organisation DATA (Debt, AIDS, Trade, Africa) in 2002. His work has won him numerous awards including the TED Prize, the NAACP Image Award's chairman's Award and was named an honorary Knight Commander of the Order of the British Empire.