The Chochenyo (also called Chocheño, Chocenyo) are one of the divisions of the indigenous Ohlone (Coastanoan) people of Northern California. The Chochenyo resided on the east side of the San Francisco Bay (the "East Bay"), primarily in what is now Alameda County, and also Contra Costa County, inland to the Mount Diablo coastal mountains.
Chochenyo (also called Chocheño and East Bay Costanoan) is also the name of their spoken language, one of the Costanoan dialects in the Utian family. Linguistically, Chochenyo, Tamyen and Ramaytush are thought to be close dialects of a single language.
The Ohlone tribes were hunter-gatherers who moved into the San Francisco Bay Region around 500 AD, displacing earlier Esselen people. In Chochenyo territory, recent datings of the ancient Emeryville Shellmounds and Newark Shellmounds attest to people residing in the Bay Area since the 4000 BC.
Chochenyo territory was bordered by the Karkin to the north (at Mount Diablo), the Tamyen to the south and southwest, the San Francisco Bay to the west, and overlapped a bit with the Bay Miwok and Yokuts to the east.
During the California Mission Era, the Chochenyos moved en masse to the Mission San Francisco de Asís (founded in 1776) in San Francisco, and Mission San José of Fremont (founded in 1797). Most moved into one of these missions and were baptized, lived and educated to be Catholic neophytes, also known as Mission Indians, until the missions were discontinued by the Mexican Government in 1834. Then the people found themselves landless. A large majority of the Chochenyo died from disease in the missions and shortly thereafter, only a fragment remaining by 1900. The speech of the last two native speakers of Chochenyo was documented in the 1920's in the unpublished fieldnotes of the Bureau of American Ethnology linguist John Peabody Harrington.
Today, the Chochenyo have joined with the other San Francisco Bay Area Ohlone people under the name of the Muwekma Ohlone Tribe. The Muwekma Ohlone are currently petitioning for U.S. federal recognition.