But have you ever wondered why we love those cats so much? Now we have an answer, in a new video from NBC News.
Ben Huh, the founder and CEO of Cheezburger, a site that shares funny viral content, says it's because humans have been breeding cats to be domestic for thousands of years.
Humans have bred cats with one desirable feature with other cats with other good features - like breeding a cute cat with a well-behaved cat. So we've been breeding them to be creatures that we love more and more.
"And instead of walking around with dogs, we socialize through the Internet," Huh explained. "And we use them as a canvas for our outlet of human emotion by adding captions to them."
So when the next cat video goes viral, now we'll know why.
Who is your favorite viral cat? Let us know in the comments below.