Maternal sepsis represents a leading cause of mortality and severe morbidity worldwide. In Italy, it is the second cause of direct maternal mortality. Delay in recognition and treatment initiation are the drivers of sepsis-associated adverse outcomes. Between November 2017 and October 2019, the Italian Obstetric Surveillance System coordinated a prospective population-based study on maternal sepsis occurring before or after childbirth from 22 weeks’ gestation onward and up to 42 days following the end of pregnancy. A nested 1:2 matched case-control study on postpartum sepsis was also performed. Maternal sepsis was diagnosed for the presence of suspected or confirmed infection alongside signs or symptoms of organ failure. The aim of this study was to assess maternal sepsis incidence and its associated risk factors, management, and perinatal outcomes. Six Italian regions, covering 48.2% of the national births, participated in the project. We identified an incidence rate of 5.5 per 10,000 maternities (95% CI 4.80–6.28). Seventy percent of patients had a low education level and one third were foreigners with a language barrier. Genital, respiratory, and urinary tract infections were the predominant sources of infection; the majority of cases was caused by E. coli and polymicrobial infections. The presence of vascular and indwelling bladder catheters was associated with a nine-fold increased risk of postpartum sepsis. There were no maternal deaths, but one fourth of women experienced a serious adverse event and 28.3% required intensive care; 1.8% of newborns died. Targeted interventions to increase awareness of maternal sepsis and its risk factors and management should be promoted.