The footage shows the big cat relaxing in the sun with the larger creature standing watch in the distance.
Without any provocation, it decides to charge at the visibly weak lion.
When the big cat tries to flee it is thrown into the air by its counterpart before hobbling away.
The remarkable incident took place in Kruger National park and was posted to YouTube on Tuesday (December 19).
Bathabile Shakwane, 22, recorded the moment and said: “A single buffalo bull seemed to notice the lion lying in the bushes and decided to tread carefully towards the lion to see what she was up to!
“At a point, the buffalo got a bit too close for comfort and the lion got a fright and tried to flee the situation.
“Once she got up, we noticed how terribly thin and weak she was looking and then I realised that this meal was a matter of life and death for her.
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“Unfortunately, in the condition she was in there was no chance she would be able to take down a healthy buffalo of that size on her own.
“The buffalo realised her vulnerable state and flung her up into the air like a rag doll.”
It comes just days after heartbreaking footage emerged of a malnourished lion fighting for its life inside a zoo.