BACKGROUND AND AIMS: Current literature on diet-constipation associations is limited by small sample sizes and cross-sectional designs. We aimed to comprehensively examine the associations between five dietary patterns, their components, and incident constipation. METHODS: In three large cohorts, the Nurses' Health Study (NHS), NHSII, and the Health Professional Follow-up Study (HPFS), we identified chronic constipation based on repeatedly-measured self-reported constipation symptoms for >/=12 weeks in the past year. We assessed long-term adherence to five dietary patterns (alternate Mediterranean diet (aMED), low-carbohydrate diet (LCD), Western diet (WD)) and indices (plant-based dietary index (PDI), empirical dietary inflammatory pattern (EDIP)) using validated quadrennial food frequency questionnaires. We used a log-binomial model adjusted for a wide range of confounders, including fiber or ultra-processed food (UPF) intake, to estimate relative risk (95% confidence interval) for constipation. RESULTS: In the pooled cohort of 27,774 (78.4+/-5.6y) NHS, 55,906 (60.5+/-4.6y) NHSII, and 12,237 (78.6+/-5.6y) HPFS participants, we documented 7,519 incident constipation cases after 2-4 years of follow-up. Compared to the lowest quintiles, the top quintiles of aMED and PDI were associated with 16% (9-22%) and 20% (14-27%) reduced risk for constipation, whereas the top quintiles of EDIP, WD, and LCD were associated with 24% (15-33%), 22% (11-33%), and 3% (-3-11%) increased risk for constipation, respectively. These associations were independent of total fiber or UPF intake. Vegetable and nut intake, which are enriched in aMED and PDI, were associated with decreased constipation risks. CONCLUSION: Our findings suggest that dietary patterns emphasizing plant-based foods and healthy fats may protect against constipation, informing future dietary interventions and treatments for chronic constipation.