The couple set up the Bill and Melinda Gates Foundation - a non-profit agency that set out to fight poverty, disease and inequity around the world - in 2000.
Mr Gates, the co-founder of Microsoft who made his fortune developing software for the personal computer, stepped down from his day-to-day role running the tech company in 2008.
The couple first met in the 1980s when Melinda joined the Microsoft firm.
Mr Gates is the fourth wealthiest person in the world, according to Forbes, and is worth $124bn (£89bn).
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The pair donated a $100M cheque to the Program for Appropriate Technology in Health in 1998
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Melinda accompanied her husband when he took the witness stand during an antitrust case against Microsoft in 2002
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Bill and Melinda took part in a discussion in Brussels in 2015 organised by British magazine The Economist about expected breakthroughs in the next 15 years in health, education, farming and banking
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Queen Elizabeth II presented Bill Gates with his honorary knighthood at Buckingham Palace in London, alongside his wife Melinda, in 2015
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Bill and Melinda met then-UN Secretary General Ban Ki-moon at the United Nations in 2015
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Then-US President Barack Obama awarded the pair the Presidential Medal of Freedom in 2016
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The couple were awarded the Légion d'Honneur - France's highest honour - by French President François Hollande in 2017 for their philanthropic efforts
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The couple enjoying a moment during a tennis match between Hubert Hurkacz of Poland and Swiss player Roger Federer in 2019