Cedros Island (Isla de Cedros, "island of cedars" in Spanish) is an island in the Pacific Ocean belonging to the state of Baja California, Mexico. The dry and rocky island had a population of 1,350 in 2005 and has an area of 348 square kilometres (134 sq mi) which includes the area of several small nearby islands. Cedros Island is mountainous, reaching a maximum elevation of 1,205 metres (3,953 ft). The economy is based on commercial fishing and salt production. Cedros has a distinctive flora and the traces of some of the earliest human beings in the New World. The ocean around the island is popular with sport fishermen.

There was human presence of the island already about 11,000 years ago. The Native American inhabitants when the island was first visited by Spanish explorers in the 16th century called it Huamalgua, the "Island of Fogs." The native inhabitants have been given the name Huamalgueños by modern day scholars. They were relocated to the mainland of Baja California by Jesuit missionaries in 1732 and ceased to exist as an identifiable people.

Cedros Island is located in Ensenada Municipality, off the west coast of the Mexican state of Baja California, from which it is separated by 100-kilometre-wide (62 mi) Sebastián Vizcaíno Bay. It is 22 km (14 mi) northwest of Punta Eugenia in Mulegé Municipality – the westernmost point of the state of Baja California Sur mainland. It also lies 15 km (9.32 mi) north of Isla Natividad (off Punta Eugenia, and also part of Mulegé Municipality) from which it is separated by the Canal de Keller, and some 500 km (311 mi) from San Diego. The island has an area of 348.295 square kilometres (134.477 sq mi), being the fourth-largest island in Mexico (following Tiburón Island, Isla Ángel de la Guarda, and Cozumel). It has a maximum length of approximately 38 km (24 mi), and a maximum width of about 17 km (11 mi).

Between Cedros Island and Isla Natividad runs the 28th parallel north, which defines the border between the Mexican states of Baja California and Baja California Sur. The Islas San Benito to the west, about 25 km (16 mi) west and 3.899 km² (1.505 sq mi) in area, are administratively part of Cedros Island.

The Isla de Cedros was named by early Spanish explorers who mistakenly associated the large amounts of redwood and cedar driftwood arriving with the California current for local pines visible on the crest of the island.

The two main elevations are Cedros hill, located at the south-center of the island, and Pico Gill to the north.

Cedros Island has a desert climate, BWh in the Köppen climate classification system and BWab (desert, hot summers, warm winters) in the Trewartha climate classification. Most precipitation occurs during the winter.

The only weather station on the island is located on the southeastern coast. The northern and western parts of the island are several degrees cooler because the cold waters surrounding the island cause heavy fog and clouds, especially during spring and summer. The condensation from the fog permits lusher vegetation to flourish, similar to the "fog oases" (lomas) of the arid Pacific Coast of South America. Precipitation is also greater at the higher elevations of the island, reaching possible annual totals of 200 millimetres (7.9 in). Rarely, heavy rains caused by unstable tropical air masses and chubascos cause flooding.