John Peter Bain, better known as Totalbiscuit, passed away on Thursday, according to his official Twitter account.
He was diagnosed with bowel cancer in 2014, a few months before his 30th birthday.
Totalbiscuit termed himself "the cynical Brit" and amassed more than 2 million subscribers with reviews, gameplay videos, and podcasts posted to his official channel.
Regular features include "Totalbiscuit suggests trying..." and "WTF is...," long-form videos which gave viewers an in-depth look at a new title, delivered in a colloquial, funny style.
His wife, Gemma Bain, posted a tribute to her husband on Thursday night, writing "Rest in Peace my Dearest Love."
She also posted the text of "Love Constant Beyond Death," a poem by the 17th-century poet Francisco de Quevedo.
On Friday morning, Totalbiscuit's subreddit, r/cynicalbritofficial/ was full of tributes from fans.
One highly-ranked post said:
"Don't think it's 'weird' that you're feeling sadness over John's passing. Even if you've never met him, his voice has been a mainstay in the gaming community for years.
"Many of us grew up with his distinct views and contributions to video games. He shaped so many minds and opinions through his sarcastic wit and no-bulls**t attitude and that's a voice that will be impossible to replace."
Totalbiscuit gave an interview on his cancer diagnosis in October 2017 to H3H3, another popular YouTube channel.
The video is here:
In the clip he said: "There's a couple of small tumours in my liver and there's one very, very small nodule in my lung. It's stage 4, which means it's spread past the initial place it was. Stage 4 is pretty bad, that's when survival chances go in the toilet."
He said he was having regular chemotherapy, which was a huge drain on him, but that he wanted to press on as long as possible, not least to keep making videos as long as possible.
"My job's a huge motivator for me. I'm proud of what I do, and I enjoy it and I know that I'm very blessed to be able to do it as a career. So I want to take every opportunity I can to do it."