BACKGROUND & AIMS: The estimated prevalence of irritable bowel syndrome (IBS) using Rome IV criteria in the United States (US) ranges from 4.7% to 5.3%, although these estimates arise from studies with relatively small sample sizes. This study assessed the prevalence of IBS and its associated burden of illness using a nationally representative data set with nearly 89,000 people in the US. METHODS: From May 3 to June 24, 2020, we performed an online survey described to participating adults aged ≥18 years old as a "national health survey." We recruited a representative sample of people in the US to complete the survey, which included the Rome IV IBS questionnaire, National Institutes of Health Patient-Reported Outcome Measurement Information System (PROMIS) gastrointestinal scales, and questions on health care-seeking behavior. RESULTS: Overall, 88,607 people completed the survey, of whom 5414 (6.1%) met Rome IV IBS criteria: mixed IBS (n = 1838 [33.9%]), constipation-predominant IBS (n = 1819 [33.6%]), diarrhea-predominant IBS (n = 1521 [28.1%]), and unsubtyped IBS (n = 236 [4.4%]). Women had higher odds for IBS compared with men, whereas racial/ethnic minorities had lower odds for IBS vs non-Hispanic Whites. Across the 3 main subtypes, 68.2% to 73.2% of people reported ever seeking care for their IBS symptoms, whereas 53.8% to 58.9% did so in the past 12 months. CONCLUSIONS: In this nationwide US survey, we found that Rome IV IBS is slightly more prevalent (6.1%) vs prior estimates (4.7%-5.3%). Additional research is needed to determine whether this higher prevalence is in part due to the coronavirus disease 2019 pandemic during which this study was conducted.