Iowa Highway 140 (Iowa 140) is a 25-mile-long (40 km) state highway in northwestern Iowa. The route begins at U.S. Route 20 (US 20) at Moville. It heads northeast and then due north; it ends at Iowa 3 near Remsen.

Iowa Highway 140 begins at U.S. Route 20 at Moville. It goes northeast through Moville towards Kingsley adjacent to the Little Sioux River. At Kingsley, Iowa 140 turns north and continues north for 16 miles (26 km) until it intersects Iowa Highway 3 southeast of Remsen, where it ends.

Iowa Highway 140 was created on 16 October 1926 from the former Iowa Highway 30, which was renumbered when the U.S. Highway System was created. Upon creation, the route was largely the same as it is today. In 1931, Iowa 140 was extended south to Hornick and west to U.S. Route 75 at Sloan. It was extended west again in 1958 when Interstate 29 was built, making its length 53 miles (85 km). In 1961, Iowa Highway 141's western end was redirected away from Sioux City and directed to Sloan via Hornick on Iowa 140. Upon this designation, Iowa 140 was truncated at Hornick. Three years later, Iowa 140 was truncated south of U.S. Route 20, to its current extent, only to be truncated north of Kingsley the next year. From 1965 to 1980, Iowa 140 was a 9-mile (14 km) long spur route. Iowa 140 was restored to its current extent in 1980.