Background Patients with irritable bowel syndrome (IBS) are often interested in dietary interventions as a means of managing their symptoms. However, the relative efficacy of available diets for the management of IBS is unclear. We aimed to examine the relative efficacy of various dietary interventions in IBS. Methods For this systematic review and network meta-analysis we searched MEDLINE, EMBASE, EMBASE Classic, and the Cochrane Central Register of Controlled Trials from database inception to Feb 7, 2025, to identify randomised controlled trials comparing an active dietary intervention requiring changes to the intake of more than one food in IBS with either a control intervention, such as a habitual diet, sham diet, a high fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet, or alternative miscellaneous dietary advice, or any other active dietary intervention requiring changes to the intake of more than one food. We assessed efficacy using dichotomous assessments of improvement in global IBS symptoms or improvement in individual IBS symptoms, including abdominal pain, abdominal bloating or distension, and bowel habit. We pooled data using a random-effects model, with the efficacy of each intervention reported as pooled relative risks (RRs) with 95% CIs. We ranked interventions according to their P-score, which measures the mean extent of certainty that one intervention is better than another, averaged over all competing interventions. Findings We identified 28 eligible randomised controlled trials (comprising 2338 patients) of 11 different dietary interventions compared with four control interventions, of which six (low FODMAP diet, British Dietetic Association/ National Institute for Health and Care Excellence [BDA/NICE] diet, lactose-reduced diet, starch-reduced and sucrose-reduced diet, a personalised diet, and a Mediterranean diet) were studied in more than one trial. For global IBS symptoms, assessed in 28 randomised controlled trials and when considering only the dietary interventions studied in more than one trial, a starch-reduced and sucrose-reduced diet ranked first (RR of global IBS symptoms not improving 0<middle dot>41 [95% CI 0<middle dot>26-0<middle dot>67]; P-score 0<middle dot>84; two trials), a low FODMAP diet ranked fourth (0<middle dot>51 [0<middle dot>37-0<middle dot>70]; P-score 0<middle dot>71; 24 trials), and a BDA/NICE diet ranked tenth (0<middle dot>62 [0<middle dot>43-0<middle dot>90]; P-score 0<middle dot>44; eight trials), versus a habitual diet. For abdominal pain, assessed in 26 trials and when considering only the dietary interventions studied in more than one randomised controlled trial, a starch-reduced and sucrose-reduced diet ranked second (RR of abdominal pain not improving 0<middle dot>54 [95% CI 0<middle dot>33-0<middle dot>90]; P-score 0<middle dot>73; two trials), and a low FODMAP diet ranked fifth (0<middle dot>61 [0<middle dot>42-0<middle dot>89]; P-score 0<middle dot>64; 23 trials), versus a habitual diet. For abdominal bloating or distension, assessed in 26 trials and when considering only the dietary interventions studied in more than one randomised trial, only a low FODMAP diet (RR of abdominal bloating or distension not improving 0<middle dot>55 [95% CI 0<middle dot>37-0<middle dot>80]; P-score 0<middle dot>64; 23 trials) was superior to a habitual diet and ranked fourth.