ABC’s long-running late-night news program "Nightline" has named a new co-anchor, replacing a co-anchor who has been on the job since 2010.

Dan Harris will take over the spot, with Bill Weir leaving ABC News. The announcement was made by ABC News boss Ben Sherwood in an email to staffers.

"I am delighted to announce that Dan Harris is becoming a co-anchor of ‘Nightline,’" Sherwood wrote. "Effective immediately, he joins Cynthia McFadden and Dan Abrams at the helm of our award-winning late night program, which recently closed out the 2012-2013 season beating its competition on CBS in every demo and consistently improving ABC’s performance at 12:35 am."

Sherwood said Weir notified him this week that he is departing ABC News for another opportunity in the news business.

Harris "will continue to co-anchor the weekend edition of ‘Good Morning America,’ a role he has held since October 2010," Sherwood wrote. "The show is posting its best ratings in years. Just last week ‘GMA Weekend’ won the 2012-2013 season as the most-watched Saturday morning program in total viewers and Adults 25-54."

Sherwood thanked Weir for his contributions to ABC News, noting: "He helped launch ‘GMA Weekend’ in 2004 and was named co-anchor of ‘Nightline’ in 2010. A gifted writer and storyteller, Bill has taken our audience around the world, reporting from atop the Golden Gate Bridge and under the waters of the Great Barrier Reef. He has ventured where few have gone before including Foxconn in China giving viewers a rare glimpse inside Apple’s factories."

Sherwood said of Harris: "Dan is one of our most versatile anchors — covering many of the biggest news stories for all of our broadcasts since he joined the network in 2000, including mass shootings in Newtown, Connecticut, Aurora, Colorado, and Tucson. He has covered natural disasters from Haiti to Myanmar to New Orleans. He has also reported from combat zones in Afghanistan, Israel, Gaza and the West Bank, and has reported from Iraq on six occasions."

Dan Harris