Westfield is a city in Plymouth County, Iowa, United States. The population was 132 at the 2010 census. It is the westernmost point in Iowa, this being due to a bend in the Big Sioux River. The nearby Broken Kettle wildlife refuge is one of the few places in Iowa where rattlesnakes are commonly found.
Westfield is the purported home town of the central character, Jack Smurch, in James Thurber's 1931 short story "The Greatest Man in the World." In the story, the fictional Smurch flies a second-hand, single-motored monoplane in July 1937 all the way around the world, without stopping.