Ehab Al Shahibi, executive director for international operations for Al-Jazeera and the man who has overseen development of the American outlet, is the interim chief executive officer.
Qatar-based Al-Jazeera, formed in 1996, has expanded quickly around the world but struggled to gain access to U.S. cable and satellite systems. At the beginning of this year, it bought former Vice-President Al Gore's Current TV, giving the company access to some 50 million homes initially, and began to set up a network specifically for the U.S. audience.
O'Brian has worked at ABC News for three decades, and since 2007 has been the network's senior vice-president for news, leading its breaking news coverage.
"She is a highly experienced and award-winning journalist who fully understands what Americans want to see and hear when they watch the news," said Mostefa Souag, acting director general of the Al-Jazeera Media Network. "Kate has the vision, tenacity and integrity to ensure that Al-Jazeera America will quickly become the success we expect it to be."
Three other Americans who have extensive experience in television news, but aren't working there currently, will join Al-Jazeera as senior vice-presidents.
David Doss, a producer for news shows at ABC and NBC News who had most recently been producing broadcasts for Anderson Cooper at CNN, will be in charge of news programming.
Marcy McGinnis, currently teaching journalism at Stony Brook University, will be responsible for news gathering, similar to a job she held at CBS News a decade ago.
Shannon High-Bassalik has run local news operations, worked at MSNBC and most recently produced CNN's morning news show before it was remodeled. She will be in charge of documentaries and programs.
Al-Jazeera has announced that a handful of familiar names to American viewers — Sheila MacVicar, Ali Velshi and Soledad O'Brien — will be doing on-air work for the network. The network also has said it will air a regular newsmagazine, "America Tonight," on weeknights.
O'Brian started work at ABC more than 30 years ago as an intern at "20/20." ABC News President Ben Sherwood wrote to his staff on Monday that "I will miss the sound of her voice, urgent and measured, calling in the middle of the night, when news is breaking somewhere around the world."