That marks CW's biggest draw in the 9 p.m. Wednesday time period since 2010, as well as its most-watched mid-season premiere since 2010. The 0.9 rating for "The 100" in the key 18-49 demographic equaled the opening of sci-fi series "The Tomorrow People" on the CW in October.
CBS' "Survivor" averaged 9.6 million viewers overall. It earned a 2.4 in the 18-49 demo, down slightly from last week, but still beating "Idol" for the second week in a row.
CBS was Wednesday's most-watched network, with 9.9 million viewers, and scored a 2.2 in 18-49, the same number as Fox.
"American Idol," in its 13th season, averaged about 9.7 million viewers over two hours, down 4% week-to-week. Its key demo rating fell 8% to a 2.2. "Idol" was Fox's only original programming in prime time.