Monday's announcement confirms recent published reports that Couric would diversify into online video programming after spending decades in broadcast television as a talk-show host and news anchor.
Couric, 56, will continue to host her daytime talk show, "Katie," on ABC even after she becomes Yahoo's "global anchor" beginning next year.
Financial terms of Couric's contract with Yahoo weren't disclosed.
The new job at Yahoo Inc. will give Couric an opportunity to report on breaking news events around the world and interview major international figures.
"Joining Yahoo offers a tremendous opportunity to reach people all around the world in the way that they're using and consuming media today," Couric said in a statement.
Couric's hiring is the latest coup for Yahoo CEO Marissa Mayer as she brings in more prominent journalists in an effort to create compelling content that will attract more people to the company's online services. In the past month, Yahoo has also lured away technology columnist David Pogue and political reporter Matt Bai from The New York Times.
Since leaving Google Inc. to become Yahoo's CEO 16 months ago, Mayer has been trying to make Yahoo's services more alluring so people will visit them on a regular basis and dwell for longer periods. In doing so, she is hoping Yahoo will be able to sell more digital ads and boost the Sunnyvale, Calif., company's lackluster revenue growth.
"Katie's depth of experience, her intellectual curiosity, and her charisma make her the perfect choice to anchor Yahoo News and the whole Yahoo Network," Mayer said. "Her unmatched energy, savvy, and versatility enables her to connect with audiences across the globe."
Couric first became a household name as a co-host of the "Today" show on NBC. She defected to CBS in 2006 to host that network's evening news.
It remains unclear whether Couric's current talk show will be renewed after its run ends in May.
The Walt Disney Co., which produces the show, and the owned and operated stations that air the program haven't decided at this point, said Bill Carroll, an expert on the syndication market for Katz Media.
Some non-ABC stations may be making the decision for her by considering deals for other talk shows that would air in Couric's time slots, including one featuring Meredith Vieira that's due to hit the airwaves next fall. Vieira replaced "Couric" on the "Today" show.
If Couric's show is to continue, it is likely to be on a smaller scale that would lower Couric's salary, Carroll said.