Background: Low back pain (LBP) is a widespread issue among postmenopausal women, significantly impacting quality of life, especially in rural and low-resource settings. Objective: This study aimed to determine the prevalence and associated risk factors of LBP in postmenopausal women aged 55 years and older in rural Bangladesh. Method: A six-month cross-sectional study, conducted from January 2023 to July 2023, included 1,000 postmenopausal women at the Gynae and Orthopedic outpatient departments of the 250-bed Sadar Hospital, Sirajganj, and North Bengal Medical College Hospital. Data were gathered through a semi-structured interview on demographics, lifestyle factors, and health status, with physical activity and self-perceived health categorized into low and high levels. Informed consent was obtained. Results: Among the 1,000 participants, 620 (62%) reported LBP. LBP prevalence was significantly higher in women with low physical activity (n = 456, 76%) compared to those with high activity levels (n = 164, 48%). Additionally, LBP was reported by 400 women (80%) with poor self-perceived health versus 220 women (45%) with good health status. A significant association was found between educational level and LBP prevalence women with primary school education (n = 320, 68%) had a higher prevalence than those with SSC-level education (n = 200, 50%) and more than SSC-level education (n = 100, 40%). Socioeconomic status and age at menopause were also significant predictors (p < 0.05). Conclusions: LBP affects a majority of postmenopausal women in rural Bangladesh, with higher prevalence among those with lower physical activity, poorer health perceptions, and lower educational attainment. Targeted community interventions are essential to reduce LBP prevalence in this population.