The Taiwanese smartphone company said that Downey Jr will be part of an ad campaign, its "most ambitious to date", with the Hollywood actor also to take part in deciding the creative direction of the campaign.
A 15-second HTC teaser ad starring Downey Jr was released onto YouTube Monday, signaling the start of the actor's reported $12 million deal with the cell phone maker, according to the Los Angeles Times.
HTC said it would be rolling out the campaign in three phases, and would highlight HTC's role as a "change maker" as well as offering a playful look at what the HTC brand means to different people.
Meanwhile the second phase will focus on HTC phone features, such as BlinkFeed, Video Highlights, and BoomSound, and Tthe final phase will promote the ways that HTC products "empower individuals to drive change in their own lives."
"HTC's innovation, authenticity, and boldness have made us the change-makers in the mobile industry and led us to launch what influencers regard as the best phone in the world, the HTC One," HTC Chief Marketing Officer Ben Ho said in a statement.
"Our original and playful Change platform is different to anything else out there and aligns our brand with the same qualities our phones are already known for."
HTC eperienced a sharp profit fall in its June quarter, despite positive reception for its HTC One flagship device, making a Marvel superhero an obvious choice to save the day.