To determine the epidemiology and microbiology of early-onset sepsis (EOS) among very preterm infants using a nationally representative cohort from academic and community hospitals to inform empirical antibiotic guidance, highlight risk factors for infection, and aid in prognostication for infected infants. Prospective observational study of very preterm infants born weighing 401 to 1500 g or at 22 to 29 weeks' gestational age from January 2018 to December 2019 in 753 Vermont Oxford Network centers. EOS was defined as a culture-confirmed bacterial infection of the blood or cerebrospinal fluid in the 3 days after birth. Demographics, clinical characteristics, and outcomes were compared between infants with and without EOS. Of 84 333 included infants, 1139 had EOS for an incidence rate of 13.5 per 1000 very preterm births (99% confidence interval CI 12.5-14.6). (538 of 1158; 46.5%) and group B (218 of 1158; 18.8%) were the most common pathogens. Infected infants had longer lengths of stay (median 92 vs 66 days) and lower rates of survival (67.5% vs 90.4%; adjusted risk ratio 0.82 95% CI 0.79-0.85) and of survival without morbidity (26.1% vs 59.4%; adjusted risk ratio 0.66 95% CI 0.60-0.72). In a nationally representative sample of very preterm infants with EOS from 2018 to 2019, approximately one-third of isolates were neither group B nor . Three-quarters of all infected infants either died or survived with a major medical morbidity. The profoundly negative impact of EOS on very preterm infants highlights the need for novel preventive strategies.