BACKGROUND AND OBJECTIVES: Population-based incidence data for dementia with Lewy bodies (DLB) remain limited, particularly using contemporary diagnostic criteria and across the full adult age range. We aimed to estimate age-specific and sex-specific incidence of DLB in a defined population and to characterize clinical features, sex-related phenotypic differences, and Alzheimer disease (AD) copathology. METHODS: We conducted a prospective, population-based incidence study in the Salento region of Southern Italy (767,356 residents) from March 1, 2023, to February 28, 2025. Incident DLB cases were identified through a multisource surveillance network and centrally adjudicated. DLB was diagnosed using the 2017 DLB Consortium criteria, with standardized assessment of all core features; AD biomarkers (CSF or amyloid PET) were incorporated when available. Incidence rates per 100,000 person-years were calculated using population denominators with Poisson 95% CIs and were directly standardized to the 2013 European Standard Population. RESULTS: Sixty-two incident DLB cases were identified over 1,534,712 person-years (mean age at diagnosis 77.4 years; 42% female). The crude incidence was 4.04 per 100,000 person-years (95% CI 3.10-5.18), and the age-standardized incidence was 3.77 (95% CI 2.89-4.83). Incidence was higher in men than women (crude 4.87 vs 3.27; standardized 4.55 vs 3.04), increased steeply with age, and peaked at 80-84 years (30.83; 95% CI 18.56-48.14). Men had greater motor severity (Movement Disorder Society-Unified Parkinson's Disease Rating Scale, part III 23.7 vs 14.4; p = 0.002), whereas women had higher neuropsychiatric burden (Neuropsychiatric Inventory total 24.0 vs 13.0; p = 0.041). Young-onset DLB (<65 years) accounted for 6.5% of cases. AD biomarkers were available in 45.2% of patients, of whom 75% were positive. DISCUSSION: In this prospective population-based study, DLB incidence increased sharply with age, peaked in the early 80s and was higher in men, with a substantial proportion of cases showing AD copathology. We also observed sex-related differences in motor and neuropsychiatric profiles. Limitations include the single-region design, incomplete biomarker testing, and lack of neuropathologic confirmation. These contemporary incidence data help quantify the burden of DLB and can inform service provision, resource allocation, and care planning in aging populations.