Femicide is an important but understudied public health and criminal justice issue. The majority of femicides in the United States are perpetrated with a firearm, and policies that may reduce firearm-related homicides are now being considered at federal and state levels. Unfortunately, there is a paucity of data on firearm ownership and homicide rates in general, and there is an even more severe lack of data on this topic as it pertains to femicide specifically. This is the first study to examine the relationship between firearm ownership and total and gender-specific, stranger versus nonstranger firearm, and total homicide rates across all 50 states during the 33-year period from 1981 through 2013, while controlling for age, gender, race/ethnicity, region, urbanization, poverty, unemployment, income, education, income inequality, divorce rate, alcohol use, nonviolent crime rate, hate crime rate, suicide rate, and incarceration rate. This study expands upon previous work by using a new and improved proxy for state-level firearm ownership and controlling for state-specific factors that could potentially confound the association between firearm ownership and homicide rates. Results demonstrate that in states where a greater proportion of the public owns firearms, there are more homicides committed, more firearm-related homicides committed, and in particular more nonstranger firearm-related homicides committed, controlling for numerous other factors that could cause spurious associations. In bivariate analyses, the strength of the association between firearm ownership rate and nonstranger firearm-related homicide rate is approximately equivalent for males and females; however, the percentage of variance in the homicide rate explained by firearm ownership is substantially higher for females (41%) compared with males (1.5%). This means that the rate of female nonstranger homicide in a state can be predicted well simply by using the prevalence of firearm ownership in that state. In controlled analyses, we found that, for each 10 percentage point increase in state-level firearm ownership in a state, the female firearm-related homicide rate increases by 10.2%, the female nonstranger homicide rate increases by 7.8%, and the overall female homicide rate increases by 7.3%. There is a specific risk of nonstranger, firearm-related femicide associated with the prevalence of firearm ownership in a state.