Arapahoe Basin (/əˈræpəhoʊ/ ə-RAP-ə-hoh; often shortened to A-Basin, or simply The Basin) is an alpine ski area in the Rocky Mountains of the United States, in the Arapaho National Forest of Colorado. Arapahoe Basin is known for its extended season and its extreme terrain. Arapahoe Basin is located south of Loveland Pass on U.S. Highway 6 in Summit County. The resort's terrain spans over 1,400 acres, serving up a mix of groomed runs, moguls, cornices, and glades. It features a lift-served vertical drop of 2,270 feet and is served by nine lifts, with easy access to 145 trails. Additionally, there is a significant amount of hike-to terrain which expands the in-bounds area appeal. There is also an abundance of non-winter activities available.

The Arapahoe Basin East Wall has a summit elevation of 13,050 feet (3,978 m), which is among the highest in-bounds skiable terrain in North America. Due to its high elevation and its mostly north-to-northeast face, the Basin's ski season is much longer than most resorts in North America. It continues to run lifts until June, sometimes lasting well into the summer, and since snowmaking was installed in 2002 it often begins its ski operations in mid-October. Its earliest opening on record was October 9, 2009, and its latest was August 10, 1995.

Arapahoe Basin is located just below Loveland Pass and offers views of the Continental Divide (which it borders) from the lifts. From the top of the ski area there are views of Lake Dillon, Breckenridge, Keystone, Montezuma, and Loveland Pass.

The Basin is located about 68 miles (109 km) west of Denver.

A-Basin has five day lodges. At the base is the "6th Alley", a year-round, day and evening restaurant/bar with indoor and outdoor dining on a two-story deck. Also, is the "Legends Cafe", a breakfast or lunch cafeteria. The "Black Mountain Lodge" sits mid-mountain, at the top of the Black Mountain Express, serving Barbecue and a day lodge style menu. "Il Rifugio" at 12,456 feet, is the highest-elevation restaurant in North America, offering a European-style bistro specializing in wine and charcuterie pairings featuring both imported and local-to-Colorado meats and cheeses. Near the top of Lenawee Lift, "Steilhang Hut" is Arapahoe Basin's newest on-mountain restaurant, serving Colorado-made specialty sausages, Colorado-brewed German draft beer, soft pretzels, and strudel made by a local Denver bakery.

There is no overnight lodging at Arapahoe Basin. The nearest lodging is located at the Keystone ski area, six miles to the west. Arapahoe Basin is also a short drive from several other towns including Breckenridge, Frisco, Dillon, Silverthorne, Silver Plume, and Georgetown.

Arapahoe Basin is mostly known for advanced and expert terrain, but also has runs for the novice and intermediate skier, as well as a children's program. The Black Mountain Express, Molly Hogan, and Pika Place & Hogan's Magic Carpet (both surface conveyors) lifts, service easy runs.

Pika Place is conveniently located close to the base area lodge and is a carpet conveyor for kids and never-evers.