INTRODUCTION: Parkinson's disease (PD) is frequently accompanied by insomnia, and emerging evidence suggests the gut microbiome may play a role. This study investigates gut microbiome differences associated with insomnia in PD patients compared to non-PD individuals. METHODS: We analyzed 310 participants (185 PD patients, 125 controls) categorized by insomnia status. Gut microbiome profiles were obtained using 16S rRNA sequencing and processed with DADA2 using the SILVA database for taxonomic assignment. Alpha and beta diversity analyses and differential abundance analysis were conducted, and functional prediction was performed using PICRUSt2, adjusting for relevant confounders. RESULTS: Insomnia was linked to higher alpha diversity in non-PD individuals but lower alpha diversity in PD patients. Interaction analysis confirmed distinct associations between insomnia and microbial diversity in the two groups. Differential abundance analysis identified unique insomnia-associated bacterial genera, with differing insomnia-risk-reducing and insomnia-risk-increasing taxa. Functional analysis showed six enriched pathways in controls but only two in PD patients, with no overlap. DISCUSSION: These findings suggest that insomnia in PD is associated with distinct gut microbiome profiles compared with non-PD individuals. The results highlight the importance of considering disease context when examining microbiome-sleep relationships and may inform future research on microbiome-based approaches for sleep disturbances in PD.