Background: Long-acting reversible contraceptives (LARCs), including hormonal implants and intrauterine devices, are highly effective pregnancy prevention methods. Aside its advantages over other hormonal methods, LARCs are cost-effective, easy to maintain, and have a low risk of non-compliance-related method failure. Besides, LARCs are also relatively safe for all sexually active women in the postpartum or post-abortion period. However, despite its effectiveness, most sexually active women use other short-term methods, such as condoms and contraceptive pills, which are associated with high discontinuation rates. Thus, this study examines the spatial distribution and multilevel factors associated with LARC use among sexually active reproductive-age women in Nigeria. Methods: This is a cross-sectional analysis of a population-based study from the 2018 Nigeria Demographic Health Survey (NDHS). The NDHS is a nationally representative survey that collects data on socio-demographic characteristics, sexual and reproductive health-related indicators such as contraceptive use and child & maternal health. A sample of 3,978 sexually active reproductive-age women (15–49 years) in Nigeria was used in the analysis. Frequency distribution and spatial analysis of LARC use were displayed with tables and maps, respectively, while multilevel analysis at a 95% confidence interval (CI) and a p-value of less than 0.05 was used to determine factors associated with LARC use among the sample. Results: The spatial distribution of LARC use among sexually active women of reproductive age in Nigeria ranges between 20 and 34.8%. Fifteen of the 36 states (excluding the Federal Capital Territory, FCT) recorded low utilization of LARCs. These states include Adamawa, Lagos, Ogun, Enugu, Anambra, Imo, Abia, Rivers, Kogi, Taraba, Yobe, Gombe, Jigawa, Borno, and Kebbi. Besides, the likelihood of LARC use was lower among participants with a prior history of pregnancy termination [aOR = 0.62; 95%(CI = 0.48–0.80)] compared to their counterparts without pregnancy termination history. Also, participants with no fertility intention had a higher likelihood of using LARCs [aOR = 1.65; 95%(CI = 1.30–2.08)] compared to those with fertility intention. At the community level, women with higher socioeconomic status were less likely to use LARCs [aOR = 0.66; 95%(CI = 0.45–0.97)] compared to women with lower socioeconomic status. Conclusions: This study showed a relatively low utilisation of LARC among sexually active reproductive-age women in Nigeria. Notably, this low utilisation is also common in states that could be described as cosmopolitan, indicating a need for closer investigation to understand context-specific factors associated with LARC use. Population-specific family planning education and counselling for this population are important to address common misconceptions about LARCs in particular and modern contraceptive use in general. [ABSTRACT FROM AUTHOR]