In the U.S. state of Wisconsin, Interstate 94 runs east–west through the western, central and southeastern portions of the state.

A total of 349.2 miles (562.0 km) of Interstate 94 lie in Wisconsin.

The route, cosigned with US 12, enters from Minnesota just east of the Twin Cities. The route passes north of Menomonie and south of Eau Claire before turning southeast and heading towards Tomah where it joins Interstate 90. The two interstates remain concurrent for the next 91.76 miles (147.67 km) to Madison. I-94 enters the state as a 6-lane facility which reduces to 4-lane at Exit 4 (US 12).

Interstate 94 passes by the popular tourist destination of Wisconsin Dells.

The route converges with Interstate 39 63 miles (101 km) southeast of Tomah (near Portage). This concurrency (30 miles) is the longest three-route concurrency of the Interstate Highway system and only one of two in existence. The interchanges mark a return to a six-lane configuration.

I-94 turns eastward toward Milwaukee at what is commonly known as the "Badger Interchange" where the three interstates meet with WIS 30. The route returns to four-lanes after the interchange traffic merges, then returns to six lanes just west of Waukesha. The highway remains six-lane facility (with various auxiliary and collector/distributor lanes in Milwaukee at interchanges) east and south of this point. I-94 passes through downtown Milwaukee, turning southbound and joining Interstate 43 for 6 miles (9.7 km).

I-94 leaves Milwaukee to the south and passes west of Racine and Kenosha on its way into Illinois toward Chicago.

I-94 was the first section of Interstate completed within the state of Wisconsin. This seven-mile (11 km) section, between the unincorporated town of Goerkes Corners (currently at the intersection of US 18 and Barker Road) and Waukesha was built in 1956. The route was added segment-by-segment over the years and was completed to its current alignment in 1968.

From 2004-2008, a portion of Interstate 94 in Milwaukee was reconstructed as a part of the Marquette Interchange project.

Beginning in 2009 and continuing until 2021, the 35 miles of Interstate 94 between the Mitchell Interchange and the Illinois state line will be widened from six to eight lanes. This includes a complete rebuild of the roadway, modern frontage roads, and interchange improvements including a new design of the Mitchell Interchange in Milwaukee County.

Two spur routes of I-94 exist in Wisconsin, both are in the Milwaukee metropolitan area.