What is the meme font?

The classic meme font that you're likely thinking of is called Impact. Impact is a standard font in most word processing programs and is easy to read overtop of images and graphics.

Impact was created in 1965 by Geoff Lee, who hand-cut the metal to create each letter. I'm not sure he could have imagined the impact (see what I did there), however, his typeface would have on popular culture.

If you want to geek out on typeface history, Vox has a nice article about the typeface and its creator.

And if you really feel compelled throw your hat into the world of memes, Kapwing has a simple template to create your own!