The celebrity world said goodbye to an American pop culture and sex icon on Friday (September 28).

On social media, stars from all corners of the industry honored the late Hugh Hefner, the iconic Playboy founder who passed away of natural causes Wednesday (September 27) at the age of 91.

A clearly shaken Pamela Anderson posted a moving video on Instagram, while other women who posed for Playboy, like Kim Kardashian, also saluted him.

But it wasn't just the women Hef worked with who took the time to acknowledge his passing. Several other big names, from TV stars and athletes to rock stars and civil rights leaders, chimed in to note how he pushed the limits of what people considered acceptable, while other lamented the loss of a pioneer who lived an amazing life.

Below, see some of the reactions to Hef's death:

Stars We Lost in 2017: