Cara Delevingne has posted a heartfelt birthday message to her close friend Rihanna calling her an inspiration.

The singer turned 26 yesterday (February 20) and Delevingne posted a photo of the two of them together to her Instagram account with the message, "Happy birthday @badgalriri

"This picture means so much to me because it was the first time we met and you have been such an incredible friend ever since. You are such a strong and truly inspiring woman and I am so lucky to have you in my life! I love you boo and thank you for supporting me through so much."

Delevingne has previously credited the Diamonds hitmaker with giving her good advice and always being there for her when she needs someone to talk to.