S4C, launched in 1982, airs more than 80 hours of programming a week, including sport, music, live events, drama, news and children's shows.
Proud has worked with production consultancy onedotzero to select directors and has chosen Rare, responsible for the latest Channel 4 rebranding, to take care of production.
Dan Witchell, former Kemistry creative director who launched Proud last year, said: "We wanted to push conventions of channel branding, and onedotzero's little black book gave us a list of directors more akin to music promos and advertising.
"The teams on both sides are looking forward to working together to progressively promote Welsh culture and language to a broader international audience."
Proud was chosen from a shortlist of five to work on the total rebrand across all media, which will include on-screen idents, print and digital media.
Dylan Griffith, S4C's creative consultant heading the rebranding process, said: "Proud's pitch matched S4C's own creative ambition and I look forward to a successful collaboration."
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