African lioness in emotional 'hug' with keeper

The lioness giving Gruener a full-blooded greeting. Credit: YouTube/Jonathan Hawkins

It's not often someone voluntarily opens an enclosure to let a big cat run at them.

But this is exactly what Valentin Gruener did in a memorable YouTube video that has now notched over 2 million views.

Far from attacking Gruener, the lioness embraces him with a full-on hug before indulging in some nuzzling reminiscent of a domestic moggy.

How did this bizarrely heartwarming scene unfold?

According to the Daily Telegraph, Gruener is one of the co-founders of the Modisa Wildlife Project in the southern African country of Botswana.

Part of his role was raising the big cats and clearly the lioness, named Sirga, had fond memories of their time together.

The man who filmed the clip, John Hawkins, wrote on his YouTube page that it was "one of the best experiences of my life" and he was "so happy" to be involved.