John Michael Scalzi II (born May 10, 1969) is an American science fiction author and former president of the Science Fiction and Fantasy Writers of America. He is best known for his Old Man's War series, three novels of which have been nominated for the Hugo Award, and for his blog Whatever, where he has written on a number of topics since 1998.

He won the Hugo Award for Best Fan Writer in 2008 based predominantly on that blog, which he has also used for several charity drives. He has written non-fiction books and columns on diverse topics such as finance, video games, films, astronomy, writing, and politics, and served as a creative consultant for the TV series Stargate Universe.

His novel Redshirts won the Hugo Award for Best Novel; his novels The Collapsing Empire and The Kaiju Preservation Society have both won the Locus Award for Best Science Fiction Novel.