In the US state of Iowa, Interstate 29 (I-29) is a north–south Interstate Highway which closely parallels the Missouri River. I-29 enters Iowa from Missouri near Hamburg and heads to the north-northwest through the Omaha–Council Bluffs and the Sioux City areas. It exits the state by crossing the Big Sioux River into South Dakota. For its entire distance through the state, I-29 runs on the flat land between the Missouri River and the Loess Hills, and is also part of the Lewis and Clark Trail.

I-29 was built in sections over a period of 15 years. When there was a shortage of male workers, female workers stepped in to build a 20-mile (32 km) section near Missouri Valley. Between Council Bluffs and Sioux City, I-29 replaced U.S. Highway 75 (US 75) as the major route in western Iowa. As a result of I-29's creation, US 75 south of Sioux City was relocated into Nebraska.

I-29 enters Iowa south of Hamburg. The Interstate heads northwest, where it meets Iowa Highway 333 (Iowa 333) at a diamond interchange. From Hamburg, I-29 continues to the northwest for seven miles (11 km) where it meets Iowa 2 three miles (4.8 km) east of Nebraska City, Nebraska. North of the Iowa 2 interchange, the Interstate straightens out to the north; interchanges serving Percival, Thurman, and Bartlett are spaced out every 4.5 miles (7.2 km). At the US 34 interchange near Glenwood, I-29 is joined by US 275.

North of Glenwood, I-29/US 275 continue north toward Council Bluffs. Near Lake Manawa, US 275 splits away from I-29 at the Iowa 92 interchange. The Interstate meets I-80 0.75 miles (1.21 km) north of the split. The two Interstates head west together through southern Council Bluffs for three miles (4.8 km) on separate carriageways. Just before I-80 crosses the Missouri River into Nebraska, I-29 immediately turns to the north. Two miles (3.2 km) to the north is a modified Y interchange with US 6 and the eastern end of I-480.

North of Council Bluffs, I-29 passes the eastern terminus of I-680 near Crescent. I-29 travels north for nine miles (14 km) before intersecting with the western terminus of I-880 near Loveland. I-29 continues north for four miles (6.4 km) to Missouri Valley, where it intersects US 30. North of Missouri Valley, the Interstate turns to the northwest toward Modale and then straightens out again south of Mondamin, where I-29 meets the western end of Iowa 127. From Mondamin, it travels north for 23 miles (37 km) to the Iowa 175 interchange at Onawa, passing Little Sioux and Blencoe.

North of Onawa, I-29 continues northwest for 15 miles (24 km) toward Sloan, where it meets the western end of Iowa 141. As it approaches the Sioux City metro area, it passes the Sioux Gateway Airport at Sergeant Bluff. At the Singing Hills Boulevard interchange, northbound is joined by southbound U.S. Highway 75 Business (US 75 Bus.). One mile (1.6 km) later, US 75 Bus. ends at the cloverleaf interchange with US 20/US 75, which is also the eastern end of I-129.

For the next three miles (4.8 km) north of the I-129 interchange, I-29 runs closely, as close as 200 feet (61 m), to the Missouri River. The Interstate follows the curve of the river and turns to the west. It meets Gordon Drive, which carries US 20 Bus. US 20 Bus. traffic is directed onto the Interstate for 0.5 miles (0.80 km) to Exit 149, which represents the national northern end of US 77. I-29 continues west along the Missouri River, and, after the Big Sioux River converges into the Missouri, I-29 follows the Big Sioux. Shortly before it crosses the Big Sioux into South Dakota, Iowa 12 splits away to the north.

Construction of I-29 began in the late 1950s in the Sioux City area. The first section to open, a three-mile-long (4.8 km) stretch from the Big Sioux River to the then–US 20/US 77 bridge across the Missouri River opened around October 1, 1958. In September 1961, I-29 was extended across the Big Sioux River to South Dakota. On April 1, 1962, some of the northbound directional spans collapsed into the Big Sioux River at the South Dakota state line as a result of flooding and bridge scour.