Actor Mia Farrow, who appeared with Attenborough in 1964's Guns at Batasi, tweeted her tribute:
Dylan McDermott, Elizabeth Perkins, and Mara Wilson – who co-starred with him in 1994's Miracle on 34th Street – expressed their sadness.
Wilson, who tragically lost co-star Robin Williams only two weeks ago, added this:
Former Labour MP Peter Hain and Labour MP Diane Abbott celebrated Attenborough's values.
Sir Roger Moore, David Cameron, and Stephen Fry added tributes:
Both Neil Gaiman and David Walliams posted clips of Attenborough in the classic British film noir Brighton Rock.
And the Academy of Motion Picture Arts and Sciences shared an inspiring Attenborough quote:
Actor Simon Pegg just shared this classic image.
And comedian Marcus Brigstocke, along with Shaun of the Dead director Edgar Wright, left reminders of Richard Attenborough's impressive body of work.