Do mountain lions eat humans? The answer is 100% No in the context of attacking a human to eat the person, in my view but I am open to disagrement. It has never happened as far as I am aware and I don’t believe that it will happen. The mountain lion is quite retiring and tends to avoid humans. Extremely rarely there have been attacks on humans by mountain lions but usually a child is involved and the attack was not to eat the child. Have you ever heard the phrase, “man-eating mountain lion” – no, nor me. We hear, in the history books, of man-eating tigers, leopards and lions but not mountain lions.
Attacks are so rare that people are far more likely to be attacked by their own domestic dog that attacked by a mountain lion. The risk is so small as to be almost insignificant although people should naturally take precautions especially with respect to their children when and where appropriate.
I suspect that the question in the title has been asked by a young person perhaps a child. In which case it is a fair question but if you know mountain lions you will know that the are not the sort of animal to attack and eat humans.
In fact, is probably fair to say that even the big wild cats (leopard, tiger, lion and jaguar) do not attack humans to eat them or extremely rarely do so. Attacks on humans are relatively, very rare and usually because the big cat is injured and unable to attack large prey or its prey has been decimated because humans have hunted its prey.
Very few animals of any species wish to eat humans. I can think of crocodiles and sharks which occasionally attack and eat humans. On the top of my head and without looking it up I can’t think of any other animal that wishes to attack, kill and eat a human (a shoal of piranhas perhaps). Some animals may attack but humans are not a natural prey of many wild animals. The human is certainly not on the mountain lion’s menu.
For the sake of completeness because the question does include all situations, I suppose if a person on a trail died and a hungry mountain lion came across his corpse the cat might eat it. The dead person would be carrion. However, that said, I can find no reference to mountain lions eating carrion in the world renowned book: Wild Cats Of The World except on one occasion a trapper was sleeping in the wilderness and when he woke up he was covered in leaves placed there by a mountain lion as if he was dead prey. He was not eaten. He shot the cat.