Billings is the most populous city in the U.S. state of Montana. The population was 117,116 at the 2020 census, while the Billings metropolitan area has an estimated 193,000 people. Located in the south-central portion of the state, it is the seat of Yellowstone County. Billings is the trade and distribution center for much of Montana east of the Continental Divide and has one of the largest trade areas in the United States. It is also the largest retail destination for much of the same area. The Billings Chamber of Commerce claims the area of commerce covers more than 125,000 square miles (320,000 km²).

Billings was nicknamed the "Magic City" because of its rapid growth from its founding as a railroad town in March 1882. The nearby Crow and Cheyenne peoples call the city Ammalapáshkuua and É'êxováhtóva respectively, meaning 'where they cut wood', named as such because of a sawmill built in the area by early white settlers. The city has experienced rapid growth and maintains a strong economy. From 1969 to 2021, the Billings area population growth was 89%, compared to Montana's overall increase of 59%. With more hotel accommodations than any area within a five-state region, the city hosts a variety of conventions, concerts, sporting events, and other rallies. It provides services to the Bakken oil development 250 to 350 miles to the east, as well as the Heath Shale oil discovery north of Billings.

Attractions in and around Billings include ZooMontana, the Yellowstone Art Museum, Pompey's Pillar, Pictograph Cave, Chief Plenty Coups State Park, Little Bighorn Battlefield, Bighorn Canyon, Red Lodge Mountain, and the Beartooth Highway. The northeast entrance to Yellowstone National Park is a little over 100 miles (160 km) from Billings.

The city is named for Frederick H. Billings, a former president of the Northern Pacific Railroad from Woodstock, Vermont. An earlier name for the area was Clark's Fork Bottom.

The Crow people from the nearby Crow Indian Reservation call the city Ammalapáshkuua. It means 'where they cut wood', and is named as such because of a sawmill built in the area by early white settlers. The Cheyenne from the nearby Northern Cheyenne Indian Reservation refer to the city as É'êxováhtóva, 'sawing place' and the Gros Ventre from the nearby Fort Belknap Indian Reservation refer to it as ʔóhuutébiθɔnɔ́ɔ́nh (lit. 'where they saw lumber'), both also named for the sawmill, or translations of the Crow name.

The downtown core and much of the rest of Billings is in the Yellowstone Valley, a canyon carved out by the Yellowstone River. Around 80 million years ago, the Billings area was on the shore of the Western Interior Seaway. The sea deposited sediment and sand around the shoreline. As the sea retreated, it left a deep layer of sand. Over millions of years, this sand was compressed into stone known as Eagle Sandstone. Over the last million years the river has carved its way down through this stone to form the canyon walls known as the Billings Rimrocks or the Rims.

The Pictograph Caves are about five miles south of downtown. These caves contain over 100 pictographs (rock paintings), the oldest of which is over 2,000 years old. Approximately 30,000 artifacts (including stone tools and weapons) have been excavated from the site. These excavations have proven the area has been occupied since at least 2600 BC until after AD 1800.

The Crow Indians have called the Billings area home since about 1700. The present-day Crow Nation is just south of Billings.