BACKGROUND: Fibrostenosis is a serious complication of eosinophilic oesophagitis, but there is a lack of consensus regarding its definition and assessment. This poses a barrier in clinical care and research. AIM: To perform a systematic review to examine existing definitions and diagnostic methods of detection regarding fibrostenosis in eosinophilic oesophagitis. METHODS: We searched MEDLINE, Cochrane Library, EMBASE, Scopus, and Web of Science and included studies of paediatric and adult eosinophilic oesophagitis patients with fibrostenosis based on endoscopy, imaging, histopathology, functional studies, and biomarkers. We excluded studies with <10 patients. We chose fibrostenosis as the umbrella term, encompassing all definitions. RESULTS: We identified 230 studies. The four categories of fibrostenosis definitions were: (1) structural findings (stricture, rings, and/or narrowings) (n=204, 88.7%), (2) histology (n=85, 37.0%), (3) functional (functional lumen imaging probe) (n=15, 6.5%), and (4) biomarkers (n=7, 3.0%). Multiple definitions were used in 78 studies. Methods used to detect structural fibrostenosis included Eosinophilic Oesophagitis Endoscopic Reference Score fibrostenotic components, luminal diameter (endoscopy or imaging), need for dilation, and endoscopist or radiologist global impression. Methods used to detect histologic fibrostenosis included Eosinophilic Oesophagitis Histologic Scoring System lamina propria fibrosis, pathologist global impression, and basal zone hyperplasia. Methods used to detect functional fibrostenosis included distensibility and compliance. CONCLUSIONS: Significant variability exists in definitions and diagnostic methods of detection regarding fibrostenosis in eosinophilic oesophagitis. Lack of agreement hampers progress in further investigating this complication. Development of consensus criteria is necessary to provide clarity for clinical care and research.