Moloka‘i (usually spelled outside Hawai‘i as Molokai) is the fifth largest island of the Hawaiian archipelago. The island is 38 by 10 miles (61 by 16 km), with a land area of 261 mile² (676 km²). It lies east of O‘ahu across the 25 mile (40 km) wide, Ka-iwi Channel and north of Lāna‘i, separated from it by the Kalohi Channel. The lights of Honolulu are visible at night from the west end of Moloka‘i, while nearby Lāna‘i and Maui are clearly visible from anywhere along the south shore of the Island.

Moloka‘i is built from two distinct volcanoes known as East Moloka‘i and the much smaller West Moloka‘i. The highest point is Kamakou on East Moloka‘i, at 4,970 feet (1,515 m). East Moloka‘i volcano, like Ko‘olau on O‘ahu is today only what remains standing of the southern half of the original mountain. The northern half suffered a catastrophic collapse and now lies as a debris field scattered northward across the Pacific Ocean bottom.

Moloka‘i is part of the State of Hawai‘i and located in Maui County, except for the Kalaupapa Peninsula , which is separately administered as Kalawao County. Maui County encompasses Maui, Lāna‘i, and Kaho‘olawe in addition to Moloka‘i. The only town of any size on the island is Kaunakakai, which is one of two small ports on the island. The airport is located on West Moloka‘i.

Moloka‘i is known as the "Friendly Isle" and is one of the least developed of the main Hawaiian islands. The island's population is diverse, with a high percentage of people of Hawaiian ancestry. Moloka‘i is noted for the numerous Hawaiian fish ponds along its south shore. Some of these have been restored in recent years. Moloka‘i contains the oldest asylum for people with leprosy in the United States (made famous by the work of Father Damien).

There are several small hotels in Kaunakakai and a resort located on the west end. Pāpōhaku Beach on the western-facing shore is one of the largest and most spectacular beaches in the Hawaiian Islands.