Paul O. Williams (January 17, 1935 – June 2, 2009) was an American science fiction writer and haiku poet.

His most notable science fiction works are a series of novels, the Pelbar Cycle, set in North America about a thousand years after a "time of fire", in which the world was nearly totally depopulated.

Much of the action takes place in the communities of the Pelbar, along the Upper Mississippi River — in the general vicinity of Elsah.

The predominant characters are change agents: Tor, Jestak, Stel and his wife Ahroe Westrun.

[1] Williams was a professor at Duke University and Principia College, and a longtime contributor to The Christian Science Monitor.