LOS ANGELES – With 125 million viewers watching more than 1 billion of its videos a month, Machinima may be the most-watched channel that’s not on TV.

The specialty channel devoted to video-game aficionados – which offers game walk-throughs, gaming news, exclusive trailers and original series – is the channel with the fourth-most subscribers on YouTube, itself the world’s third-most-popular website, according to online measurement firm ComScore Inc.

Machinima may represent the next best hope of programming to the so-called Lost Boys, those young male consumers, once Hollywood’s most dependable audience, who are increasingly reluctant to leave their video-game consoles and Facebook pages to watch movies and TV or listen to music. It may also rewrite the rules for Internet programming.

“You could argue that Machinima is to gaming what MTV was to music in its early days,” said Michael E. Kassan, chairman and chief executive of MediaLink, an influential digital-media consulting firm.

The channel got its start in 2000 as a website for filmmakers using video-game environments and characters to create original stories. In 2005, brothers Allen and Philip DeBevoise acquired the website and turned it into a destination for gaming and gaming culture.

Machinima has reached beyond its roots. Last year, it introduced live-action programs, including the zombie apocalypse show “Bite Me” and the retro “X-Files” show “RCVR.” The shows’ appeal, and the Internet’s borderless reach, has given Machinima enviable distribution for original programming.

“With YouTube and the platforms on the Internet, they’re in every country and on every device. It means we are instantly global,” said Machinima Inc. Chief Executive Allen DeBevoise.

Machinima is part of what’s been called the “third wave” in video entertainment, each part of which revolutionized the entertainment industry, DeBevoise said. ABC, CBS and NBC dominated the broadcast-television era. Cable and satellite technology opened the doors to new, more specialized entertainment channels, including HBO, ESPN, MTV and CNN. Now the Internet is poised to overturn the reigning paradigm yet again, he said.

Machinima would appear to be proof that YouTube’s global reach – 800 million users who watch 4 billion videos a day – allows programmers to amass sizable audiences around niches.

“Machinima has done an impressive job building one of the largest channels on YouTube, with a viewership that rivals the top 20 cable networks,” said Robert Kyncl, global head of content for YouTube parent company Google Inc. “They’re successful because they understand their fans and deliver to them the content they love.”

With YouTube’s help, he said, Machinima “can reach a global audience with the click of a button.”

The size of Machinima’s audience has not gone unnoticed by advertisers.

Telecommunications giant Verizon Communications Inc. used the gaming network to promote the availability of a selection of live FiOS TV channels over Microsoft’s Xbox 360 console. Consumer products colossus Unilever made Machinima, with its heavy concentration of male viewers ages 13 to 34, a part of its Premature Perspiration campaign to promote Axe antiperspirant.

Wired magazine first reported in 2004 on the Lost Boys – men ages 18 to 34 who were migrating away from TV and spending more time online, watching DVDs or playing video games. Although a majority of them still watch five hours or more of TV a day, according to the annual Magid Media Futures of TV study, 18 percent say they view one hour or less a day.

“Machinima reaches a notoriously difficult group of viewers,” said Tim Hanlon, founder and chief executive of the Vertere Group, an emerging-media consulting firm in Chicago.

Now Machinima has the attention of Wall Street. In December, the company retained the investment firm Allen & Co. in an effort to raise $25 million. The money is intended to finance the acquisition and creation of more premium content, bolster the company’s ad sales team and develop technology, said Sanjay Sharma, Machinima’s senior vice president of business development.

Industry insiders speculate that Machinima is looking to extend its already-popular brand across additional platforms, such as Facebook, or to smartphones and tablets powered by Apple or Google software.

“You’re going to watch Machinima take the base that they’ve built, which is extraordinary, and build it further with original programming,” MediaLink’s Kassan said. “Machinima may be that success story that people point to … the first company to break through (on YouTube) to the next level.”