ImportanceFirearm violence is a major public health problem in the US. However, relatively little research has focused particular attention on firearm violence in rural areas, and few studies have used research designs that draw on exogenous variation in the prevalence of firearms to estimate the association between firearm presence and shootings.ObjectiveTo investigate the association between the start of deer hunting season and shootings in rural counties in the US.Design, Setting, and ParticipantsIn this cohort study, data from all rural US counties in states with available data on the timing of deer hunting season were matched with data on shootings from the Gun Violence Archive from January 1, 2014, to December 31, 2021.ExposureShootings in the first 3 weeks of deer hunting season were compared with the week prior to the start of deer hunting season.Main Outcomes and MeasuresThe main outcome was daily total shootings. The association between the start of deer hunting season and shootings was estimated using Poisson regression models to analyze change within counties while controlling for relevant calendar year, month of year, and seasonal effects.ResultsThe sample included 854 rural counties with a mean (SD) population of 16 416 (18 329) per county and 5.4 (13.3) annual shootings per 100 000 people. The county fixed-effects specification analyzing the association between deer hunting season and shootings showed that relative to the week prior to deer hunting season, the incidence rate ratio for total shootings was 1.49 (95% CI, 1.13-1.95) for the first week of deer hunting season and 1.41 (95% CI, 1.02-1.94) for the second week of deer hunting season. Estimates remained consistent when excluding hunting accidents and were most pronounced in states with more hunting licenses per capita.Conclusions and RelevanceIn this cohort study of the association between the start of deer hunting season and firearm violence, results showed that the start of deer hunting season was associated with a substantial increase in shootings. The findings highlight the role of firearm prevalence in gun violence and suggest the need for focused policies designed to reduce firearm violence in areas with substantial hunting activity during the first weeks of deer hunting season.