The annual Great Gorilla Run is an 8km route though the City of London, starting at Minster Court.
Since the first run in 2003, thousands of people have donned fancy dress in order to raise money for gorilla conservation and poverty reduction projects in central Africa.
And this year's event saw gorillas in all sorts of unusual situations.
There were gorillas posing in bikinis.
Yep, there were plenty of selfies going on, obvs.
A gorilla in a Santa suit... because it's never too early in the year for that.
There were some seemingly patriotic gorillas taking part.
Of course there were cardboard skyscraper props.
And there was this look of terror... honestly, we have no idea what's going on here either.
But one thing we do know is boy, does it look hot and sweaty for the people inside those suits... *applauds every fun runner*