Race and ethnicity in the United States Census, as defined by the United States Census Bureau and the Federal Office of Management and Budget (OMB), are self-identification data items in which residents choose the race or races with which they most closely identify, and indicate whether or not they are of Hispanic or Latino origin (ethnicity).

The racial categories represent a social-political construct for the race or races that respondents consider themselves to be and "generally reflect a social definition of race recognized in this country." The OMB defines the concept of race as outlined for the US Census as not "scientific or anthropological" and takes into account "social and cultural characteristics as well as ancestry" using "appropriate scientific methodologies" but not "primarily biological or genetic in reference."

Race and ethnicity are considered separate and distinct identities, with Hispanic or Latino origin asked as a separate question. Thus, in addition to their race or races, all respondents are categorized by membership in one of two ethnicities, which are "Hispanic or Latino" and "Not Hispanic or Latino". In 1997, OMB issued a Federal Register Notice which provided revised racial and ethnic definitions. OMB developed race and ethnic standards in order to provide "consistent data on race and ethnicity throughout the Federal Government. The development of the data standards stem in large measure from new responsibilities to enforce civil rights laws." Among the changes, OMB issued the instruction to "mark one or more races", after noting evidence of increasing numbers of interracial children and the desire to capture this increased diversity in a measurable way. Prior to this decision, the Census and other government data collections asked people to report only one race.

"The categories are designed for collecting data on the race and ethnicity of broad population groups in this country. They are based on social and political considerations -- not anthropological or scientific ones. Furthermore, the race categories include both racial and national-origin groups.”