Wilby is an unincorporated community in northern Butler County, in the U.S. state of Missouri.^[1] The community is on Missouri Route O approximately seven miles north of Poplar Bluff. It sits on the east margin of the Black River floodplain^[2] at an elevation of 361 feet.^[1] The community of Hilliard lies three miles to the south-southeast along the Black River.^[3] The Missouri Pacific Railway passes the west side of the community along the Black River floodplain. The community lies within the Mark Twain National Forest.^[2]

The community most likely was named after Wilby, a railroad employee.^[4]