The actor and producer was originally booked on one of the flights that hit the World Trade Center. However, he changed his plans last minute, narrowly avoiding the tragedy.
Before becoming famous, he was a New York City firefighter. He returned to his old job and volunteered at Ground Zero to find survivors and remains.
The British monarch was visiting New York City at the time of the attacks. She made a historic speech expressing her sympathy and support for the victims and their families.
The former Mayor of New York City, Rudy Giuliani, played a crucial role in leading the city through the aftermath of 9/11 and coordinating rescue efforts.
The actress had a personal connection to the events, losing her close friend and fellow actor, Michael Olifier, in the attacks.
The King of Pop was deeply affected by the events and released a charity single called "What More Can I Give?" to raise funds for the victims and their families.
The action star was in New York City during the attacks and supported the relief efforts by raising funds and lending his voice to raise awareness.
He is not a traditional celebrity, but Howard Lutnick, CEO of Cantor Fitzgerald, lost his brother and nearly 700 employees in the World Trade Center attacks.
The "Law & Order: SVU" star lost her close friend and mentor, actress Mary McCormack, in the attacks.