Maternal autoimmune diseases (AIDs) have been linked to adverse birth outcomes that may potentially increase cardiovascular disease (CVD) risk in offspring. However, whether maternal AIDs is associated with offspring CVD remains largely unexplored. This study aimed to examine whether intrauterine exposure to maternal AIDs is associated with offspring CVD up to early adulthood. This nationwide population-based cohort study included 1 455 645 live singleton births during 2001-2014 in Sweden and followed them to 31 December 2023. Associations between maternal AIDs and offspring CVD were evaluated using Cox proportional hazard models. Cousin analyses and analyses with paternal AID were conducted to assess shared genetic and familial environmental confounding. During a median follow-up of 15.2 years (range, 0-23.7 years), 90 046 (6.2%) participants were exposed to maternal AIDs and 40 260 (2.8%) were diagnosed with CVD. Intrauterine exposure to maternal AIDs was associated with an increased risk of any CVD in offspring (hazard ratio 1.19, 95% confidence interval 1.14-1.24). Elevated CVD risks in offspring were observed across maternal AID categories. Paternal AIDs had a weaker association with offspring CVD than maternal AIDs; the associations in the cousin analyses persisted, though they were somewhat weaker than those in the main analyses. Maternal AIDs is associated with a moderately increased risk of CVD in childhood and early adulthood in offspring. These findings need to be interpreted with caution, as shared familial factors may partly contribute to the observed associations, and further studies are needed to clarify the mechanisms underlying the observed associations.