David Jason Muir ( MURE; born November 8, 1973) is an American journalist and anchor for ABC World News Tonight and co-anchor of the ABC News magazine 20/20, part of the news department of the ABC broadcast-television network, based in New York City. Muir previously served as the weekend anchor and primary substitute anchor on ABC's World News Tonight with Diane Sawyer before succeeding her on September 1, 2014.

Since joining ABC News in 2003, Muir has reported from international hotspots all over the world, with dispatches from Afghanistan, Iraq, Iran, Ukraine, Tahrir Square, Mogadishu, Gaza, Guantanamo, Fukushima, Beirut, Amman, and the Syrian border, among other locations. At ABC News, Muir has won multiple Emmy and Edward R. Murrow awards for his national and international journalism. He was the 2024 recipient of the Walter Cronkite Award for Excellence in Journalism. Muir won the Emmy for Outstanding Live News Program in both 2023 and 2024 and won the Edward R. Murrow Award for Network TV Newscast in the same years.

Muir has become one of the most visible journalists in America. World News Tonight with David Muir has been the most watched newscast in the United States since 2015. Muir's climate reporting has also been recognized with the George Polk Award, and the Alfred I. duPont-Columbia Award.