路易氏体型失智症（英语：Dementia with Lewy bodies，缩写为 DLB），失智症的一种，患病人数排名第二高，仅次于阿兹海默症。目前的估计，被诊断是失智症的患者中有大约60%至70%是阿滋海默氏症或是与脑血管疾病式的混合种，有10%至15%是路易氏体型失智症，剩下的分布于其他各式各样的失智症包括了额颞叶退化、酗酒失智、血管疾病失智。

Dementia with Lewy bodies (DLB), also known as Lewy body dementia (LBD), diffuse Lewy body disease, cortical Lewy body disease, and senile dementia of Lewy type, is a type of progressive neurodegenerative dementia closely associated with Parkinson's disease primarily affecting older adults. Its primary feature is cognitive decline, which can lead to hallucinations, as well as varied attention and alertness when compared to a person's baseline function.