Charles Gibson will step down as news anchor on ABC television's World News and will be replaced by Diane Sawyer beginning in January, ABC News said on Wednesday.
Sawyer's promotion means two of the three big U.S. network nightly newscasts will be in the hands of women anchors. Katie Couric heads up CBS Evening News.
Sawyer, most recently a host of ABC's Good Morning America show, was a pioneer among women in American broadcast television news, becoming the first woman to co-anchor the top-rated 60 Minutes news magazine on CBS before joining ABC News in 1989.
Gibson has served as the news program host since May 2006 and will retire after a 40-year career in television in which he has moderated presidential debates and reported from around the world.
Since the advent of cable and satellite television, national broadcast news has lost much of the formidable influence it once had over U.S. politics and current affairs, but the network news anchor positions are still viewed as benchmarks for the profession.
Three years ago, Couric left NBC's Today show to take the anchor spot on CBS Evening News, becoming the first solo female anchor of a U.S. network nightly newscast.
Couric saw a boost in ratings for Evening News when she first joined the program, but since then she has endured more lackluster viewership.
Last year, Couric denied reports she was leaving the newscast, and she earned praise for hard-hitting interviews with then Republican vice presidential candidate Sarah Palin.
ABC is a unit of Walt Disney Co.