Materials and Methods: This cross-sectional study included 240 women aged 18–65 years who met the 2016 American College of Rheumatology criteria for FM and reported lower urinary tract symptoms for at least three months. OAB was diagnosed based on International Continence Society criteria using the OAB-V8 questionnaire (cut-off ≥8) and a three-day bladder diary. Psychiatric symptoms were assessed using the Hospital Anxiety and Depression Scale (HADS). FM severity was measured using the Widespread Pain Index (WPI), Symptom Severity Scale (SSS), and General Symptom Score (GSS). Patients were divided into FM+OAB and FM−OAB groups. Statistical comparisons and correlation analyses were performed.

Results: OAB was identified in 148 of 240 FM patients (61.7%). The FM+OAB group had significantly higher mean age (47.2 ± 7.4 vs. 41.5 ± 10.1 years, p < 0.001) and fibromyalgia diagnosis time (10.5 ± 8.7 vs. 6.3 ± 6.0 years, p < 0.001) compared to the FM−OAB group. Clinically significant anxiety and depression (HADS ≥8) were more prevalent in the FM+OAB group (52.1% vs. 27.3%, p = 0.006). FM+OAB patients also had higher scores for WPI, SSS, and GSS (all p < 0.001). HADS scores correlated positively with FM symptom severity and OAB-V8 scores (ρ = 0.30–0.42, p < 0.01).

Conclusion: Overactive bladder is highly prevalent among women with fibromyalgia and is associated with greater psychiatric burden and symptom severity. These findings suggest a shared underlying mechanism driven by central sensitization and emotional dysregulation. Routine screening for OAB and psychological distress in FM patients may enhance diagnostic accuracy and guide comprehensive, multidisciplinary treatment strategies.