Frequently Occurring Last Names in the 2020 Census is the fifth U.S. Census Bureau data product listing the most common last names reported in the decennial census. A 1909 report (Bureau of the Census 1909) provided extensive data on “surnames of the white population” tabulated in the 1790 Census. The modern series of data releases began with the 1990 Census, but the 1990 data tables were based on results from the post-enumeration survey rather than the census itself (U.S. Census Bureau, 1995). The 2000 product used full census results and applied very different methods from the 1990 release (Word et al., 2007). The 2000 methodology was revised for the 2010 product (Comenetz, 2016) and further revised and expanded for 2020. This document first summarizes the methodological changes between 2010 and 2020, then describes the 2020 results and compares them with data from previous decades.