Prince Philip's most memorable moments

Prince Philip turns 99 today. The royal, who retired from official duties in 2017, is expected to spend a quiet day at Windsor Castle, where he has been self-isolating with the Queen since March.

While Philip has been forced to slow down in recent years, he certainly made an impact over the decades.

Standing steadfastly by Queen Elizabeth's side during her reign, he quickly became known for speaking his mind.

Here is a compilation of his greatest gaffes that the unapologetic prince became known for.

WATCH THE VIDEO ABOVE.