Aniston who co-starred alongside Cox as Rachel Green and Monica Geller in the popular US sitcom from 1994 to 2004 respectively, said that it was one of the "great honours to call her one of my best friends for life".
Taking to Instagram, Aniston shared several images of herself and Cox, including a clip of them from a Friends scene, as well as a Facetime call, blowing each other kisses. The images also appear to show Cox's daughter Coco Arquette, who is reportedly Aniston's god daughter.
"Celebrating this powerful, magical, mystical, interesting, interested, ferociously talented girl today!!! My sweet CC @courteneycoxofficial… she's funny like no other, stunning on the inside and out", Aniston wrote in Cox's honour.
"Independent in the most gorgeous way, cares for everyone even if she doesn’t know you", she added. "Terrified of dogs even though I’ve never known her not to have at least two of them. Fiercely loyal to the end.
"She’ll redecorate a room like nobody’s business. Spot a smudge on a window from a mile (literally) away. She doesn’t care what other people think!! I can’t imagine a world without her. It’s one of my great honours to call her one of my best friends for life… Happy happy birthday CC. I love you!".
Check it out below.
