The Anti-Vagrancy Act, also known as the Greaser Act, was enacted in 1855 in California, legalizing the arrest of those perceived as violating its anti-vagrancy statute.

The law is sometimes referred to as the Greaser Act because the law uses the word "Greaser", found in section two, to refer to individuals of "Spanish and Indian blood."

The end of the Mexican–American War in 1848 was marked by the Treaty of Guadalupe Hidalgo, which resulted in Mexico's cession of the Southwest, leading to the United States' acquisition of California, Colorado, Nevada, New Mexico, Texas, Utah, Arizona, and Wyoming. As elaborated by Latino History and Culture: An Encyclopedia, "Euro-Americans were eager to solidify their power in the region they had just taken from Mexico," and thus began to construct a legal and economic system to develop the Southwest.

California underwent much development during the late 1840s and early 1850s, especially due to the economic boom produced by the gold rush between the years 1840 and 1855. Some have characterized the sentiments of this era as being a consequence of the economic development; for example, scholar Leonard Pitt has described that "nativism was born in the months of 1849 and early 1850 when mining enterprise was most individualistic, government most ineffectual, and immigration most rapid."

Tensions mounted in the region, catalyzing both vigilante justice and legal discrimination against minority groups to retain European American interests in the region. The Greaser Act is part of a history of anti-immigration (e.g. Chinese Exclusion Act) and discriminatory laws passed in the Southwest (e.g. Foreign Miners' Tax). The Foreign Miners' Tax of 1850, which called for all non-European non-citizen miners to pay a tax in order to work in the mines, can be considered "a system of taxation and indenture...to exploit alien caste laborers rather than expel them."

Under "An Act for the Government and Protection of Indians", passed in 1850, Native Americans in California were targeted under the guise of stopping vagrancy and promoting apprenticeship. As outlined by the California Research Bureau of the California State Library, the act "facilitated removing California Indians from their traditional lands, separating at least a generation of children and adults from their families, languages, and cultures...and indenturing Indian children and adults to Whites." The Anti-Vagrancy Act of 1855 extended the vagrancy statutes to non-Native Americans in a less severe manner.

The original title of the act clearly states that its purpose is "To punish Vagrants, Vagabonds, and Dangerous and Suspicious Persons." Six short sections outline the punishment at first incident, the protocol for disarming greasers, the consequences of a second conviction, the potential avenues of employment for vagrant, the discharge procedures and the timeline for when the act is to go into effect. The law defined a vagrant as including all those who do not have or accept employment, prostitutes and drunkards and calls for their incarceration for up to ninety days; during this time they may be "sentenced to hard labor."

Section 2 identifies people by ethnoracial background by referring to "all persons who are commonly known as 'Greasers' or the issue of Spanish and Indian blood... and who go armed and are not peaceable and quiet persons." The word "greaser" (a vestige of the Mexican–American War) was a derogatory term used to refer to Mexicans and Mexican Americans referring to "the practice of Mexican laborers in the Southwest greasing their backs to facilitate the unloading of hides and cargo," their skin color, or presumptions about their hygiene.