Ishikawa Prefecture (石川県, Ishikawa-ken; Japanese pronunciation: [i.ɕi̥.ka.wa, -waꜜ.keɴ]) is a prefecture of Japan located in the Chūbu region of Honshu island. Ishikawa Prefecture has a population of 1,096,721 (1 January 2025) and has a geographic area of 4,191 km² (1618 sq mi). Ishikawa Prefecture borders Toyama Prefecture to the east, Gifu Prefecture to the southeast, and Fukui Prefecture to the south.

Kanazawa is the capital and largest city of Ishikawa Prefecture, with other major cities including Hakusan, Komatsu, and Kaga. Ishikawa is located on the Sea of Japan coast and features most of the Noto Peninsula which forms Toyama Bay, one of the largest bays in Japan. Ishikawa Prefecture is part of the historic Hokuriku region and formerly an important populated center that contained some of the wealthiest han (domains) of the Japanese feudal era. Ishikawa Prefecture is home to Kanazawa Castle, Kenroku-en one of the Three Great Gardens of Japan, Nyotaimori ("body sushi"), and Kutani ware.

Ishikawa was formed in 1872 from the merger of Kaga Province and the smaller Noto Province, with the seat of the government being located in Mikawa. The political center of Ishikawa was moved to Kanazawa in 1873.

The newly formed Ishikawa Prefecture came to be regarded with caution by the national government following the Kioizaka Incident [ja] in 1878, in which 6 shizoku (士族), dissatisfied by the Meiji government's "maladministration, suppression of civil rights, and misuse of government property", assassinated Japanese statesman Ōkubo Toshimichi. Concerned about the possibility of a Hokuriku bloc forming in support of the Freedom and People's Rights Movement, and thus wanting to weaken the influence of the former Kaga lords, the national government made the decision to divide the prefecture. This took place in two stages, beginning in 1881, when Fukui Prefecture was formed, and ending in 1883 with the formation of Toyama Prefecture.

On 1 January 2024, a 7.5 magnitude earthquake struck Ishikawa Prefecture, specifically the Noto Peninsula. In Ishikawa, a total of 508 people were killed and 2 people are currently reported missing as a result of the earthquake. Overall it is estimated that 1,200 people were injured across different prefectures.

In September 2024, severe rainfall in the prefecture led to deadly floods and landslides, causing at least six deaths and widespread damage. Thousands were evacuated as rivers overflowed, while recovery from a prior earthquake complicated relief efforts. Emergency warnings remain in place.

Ishikawa is on the Sea of Japan coast. The northern part of the prefecture consists of the narrow Noto Peninsula, while the southern part is wider and consists mostly of mountains with the prefecture's chief city, Kanazawa, located in the coastal plain. The prefecture also has some islands, including Notojima, Mitsukejima, Hegurajima.

As of 1 April 2012^[update], 13% of the total land area of the prefecture was designated as Natural Parks, namely the Hakusan National Park; Echizen-Kaga Kaigan and Noto Hantō Quasi-national parks; and five prefectural natural parks.