Felix Kjellberg, better known by his online alias PewDiePie, earned 63 million SEK (around $7.5 million) in 2014, according to financial documents.
PewDiePie is famous for his Let's Play videos, in which he runs through a game whilst providing his own opinions, often coupled with over-the-top reactions. He also releases short comedy sketches and partners with other big YouTubers on content.
Kjellberg created PewDiePie six years ago and, in December of 2012, he signed a deal with online video content creator Maker Studios, which is now owned by Disney.
He currently has 37 million subscribers and generates over $4 million in ad sales per year.
In 2014, Kjellberg said his videos, in some ways, are designed to encourage developers to create games that are not only fun to play, but to also fun for others to watch.
"It's cool to have this kind of influence, but at the same time it's kind of scary," Kjellberg said.
According to Kjellberg, the original name for his YouTube account was PewDie ("pew" for the sound of a laser gun and "die" for death), but after he lost his account password he had to come up with a new name, so he added "Pie" to it.
He also said his popularity on YouTube is somewhat unsettling: "I'm so central to YouTube now, and that puts me in the spotlight and raises a lot of questions like 'Why is he so big?'" Kjellberg said. "I'd much rather prefer to have something like 5 million subscribers."