The Pearl and Hermes Atoll (Hawaiian Holoikauaua), also known as Pearl and Hermes Reef, is part of the Northwestern Hawaiian Islands, a group of small islands and atolls that form the farthest northwest portion of the Hawaiian island chain. The atoll consists of a variable number of flat and sandy islets, typically between five and seven. More were noted in historical sources but have since been lost to erosion and rising sea levels.

The atoll is named after Pearl and Hermes, a pair of English whaleships that wrecked there in 1822. It has been the site of at least eight known shipwrecks, including the Japanese Wiji Maru, SS Quartette, and most recently MV Casitas, which ran aground on the reef in 2005.

The atoll is an important habitat for seabirds, marine life, and invertebrate species. Twenty-two bird species nest and breed on the islands, including twenty percent of the world's population of black-footed albatrosses. The atoll has historically been included with the rest of the Northwestern Hawaiian Islands in conservation efforts. It is included in the Papahānaumokuākea Marine National Monument, created in 2006. Ghost nets and other fishing debris, rising sea levels, and the invasive algae Chondria tumulosa pose a significant risk to the atoll and its wildlife.

The Pearl and Hermes Atoll is the third northernmost atoll of Hawaii, behind Midway and Kure, approximately 1,299 mi (2,090 km) northwest of Honolulu and 87 mi (140 km) east-southeast of Midway Atoll. Like the rest of the Hawaiian Islands, the atoll observes Hawaii Standard Time. In total, Pearl and Hermes has about 32 ha (80 acres) of land and almost 80,937 ha (200,000 acres) of coral reef habitat. The fringing coral reef which surrounds the atoll is roughly 43 mi (69 km) in circumference and open to the west.

The atoll's land area consists of several small islands which are periodically washed over when winter storms pass, along with several ephemeral sand spits. The islets are low and flat, with an average elevation of no more than 1.2 metres (3.9 ft) in 2012, and there are no sources of fresh water on any of them. As of 2012, according to the United States Geological Survey (USGS), the atoll consists of five islands. Earlier sources note the presence of other islets, including a Sand Island and a Bird Island.

From largest to smallest, the five remaining islands are Southeast Island (18.4 ha (45 acres)), Seal-Kittery (13.7 ha (34 acres)), North Island (8.4 ha (21 acres)), Grass Island (3.2 ha (7.9 acres)), and Little North Island (3.2 ha (7.9 acres)). Only the three largest islands have vegetation.

Comma-shaped North Island is the atoll's northernmost island. Little North Island lies to the southeast, less than 1 km (0.62 mi) away. Southeast Island lies approximately 15 km (9.3 mi) to the southeast of Little North. Grass Island approximately 9 km (5.6 mi) east, and Seal Kittery just under 4 km (2.5 mi) to the east of that.

The atoll is named for the ships Pearl and Hermes, which were wrecked upon it in 1822.