Forest Whitaker, Serena Williams and Zendaya are among stars who paid tribute.

In honor of the late Nelson Mandela, Hollywood A-listers paid tribute to the philanthropist via social media on internationally celebrated Nelson Mandela Day.

On what would have been Mandela's 97th birthday, stars posted photos and quotes July 18 in remembrance of the first president of South Africa. The United Nations officially declared it an international day in November 2009; July 18, 2010, was the first official Nelson Mandela Day.

See the heartfelt tributes below.

"Sometimes it falls upon a generation to be great...Let your greatness blossom." @NelsonMandela #MandelaDay2015 pic.twitter.com/rD8IvwornR

— Muhammad Ali (@MuhammadAli) July 18, 2015

It is in your hands to make of our world a better 1 for all,especially the poor, vulnerable&marginalised #MandelaDay pic.twitter.com/ZKu3UYBaXs

— NelsonMandela (@NelsonMandela) July 18, 2015

#NelsonMandela teaches us that a common humanity means we can only achieve true freedom by forgiving those who've done us the greatest harm

— Forest Whitaker (@ForestWhitaker) July 18, 2015

 

Nelson Mandela was great man, and I realized is still inspiring me and many others. Forgiveness is vital to let our minds not stay in a mental prison. It doesn't matter how ignorance may affect you, let's inspire and lift one another up. I'm so fortunate to have met him. #mandeladay

A photo posted by Serena Williams (@serenawilliams) on Jul 18, 2015 at 9:31am PDT

"It always seems Impossible, until it's Done!" -@NelsonMandela #MandelaDay @winniemandela pic.twitter.com/PQI9UIk1Ef

— TD Jakes (@BishopJakes) July 18, 2015

Happy Mandela Day from South Africa...go out there and continue his legacy #bemoremadiba #67 https://t.co/df8cJTpHZH

— Zendaya (@Zendaya) July 18, 2015

 

Happy Mandela Day from South Africa...go out there and continue his legacy #bemoremadiba #67

A photo posted by Zendaya (@zendaya) on Jul 18, 2015 at 4:04am PDT

 

Nelson Mandela was great man, and I realized is still inspiring me and many others. Forgiveness is vital to let our minds not stay in a mental prison. It doesn't matter how ignorance may affect you, let's inspire and lift one another up. I'm so fortunate to have met him.#mandeladay

A photo posted by Serena Williams (@serenawilliams) on Jul 18, 2015 at 9:31am PDT

How we can all live out Nelson Mandela's tremendous dream for humanity: http://t.co/baPmQsPlYD pic.twitter.com/U8D4t7gVt3

— Richard Branson (@richardbranson) July 17, 2015

"Mandela showed us the power of action; of taking risks on behalf of our ideals." —President Obama: http://t.co/FHaSpdBbGU #MandelaDay

— The White House (@WhiteHouse) July 18, 2015

 

#MandelaDay. A look back at Madiba's life & legacy, in pictures http://t.co/p97bWfTbEa pic.twitter.com/OFVhHBuPRU h/t @GettyImages /via @heykim

— Alyssa Milano (@Alyssa_Milano) July 18, 2015

Happy Birthday to a true hero, Nelson Mandela.#MandelaDay pic.twitter.com/hfmgKaaB9f

— OprahWinfrey Network (@OWNTV) July 18, 2015

More to come...