Background: Metabolic dysfunction-associated fatty liver disease (MAFLD) has garnered increasing attention for its potential link with dementia. This study aims to investigate the association between MAFLD and dementia, including its subtypes, to address existing knowledge gaps. Methods: A total of 415,116 participants from the UK Biobank were included, with standardized screening criteria used to determine MAFLD diagnosis. Cox regression was employed to assess the relationship between MAFLD and dementia risk. Subgroup analyzes were conducted to provide further insights into the impact of MAFLD on dementia risk, and the mediation effect of inflammation was evaluated. Results: Among the 150,509 MAFLD patients, there was a significantly elevated risk of dementia, with hazard ratios (HR) of 1. 526 (95 % CI = 1. 460-1. 596) for all-cause dementia, 1. 356 (95 % CI = 1. 266-1. 453) for Alzheimer's disease (AD), and 2. 206 (95 % CI = 2. 000-2. 434) for vascular dementia (VaD). MAFLD patients showed a significant reduction in gray matter volume in MAFLD patients (beta = -0. 07, 95 % CI = -0. 17, -0. 01) and a marked increase in deep white matter lesion volume (P < 0. 001). Elevated inflammatory markers in MAFLD patients accounted for a mediation effect of 30. 8 %. Conclusion: MAFLD substantially increases the risk of dementia, underscoring the importance of early intervention and prevention strategies targeting MAFLD to reduce dementia incidence.