Monazite is a phosphate mineral, considered an essential source of light rare-earth elements (REE). The present work sought to evaluate different methods of solubilization of REE through the use of different concentrations of inorganic acids (H2SO4, HCl, and HNO3) and organic acids (citric, oxalic, and lactic) in mild conditions at room temperature. According to the results, the inorganic acid solutions favored the solubilization in order of Ce3+, La3+, Nd3+, Pr3+, and Sm3+ elements, while organic acid solutions only favored the solubilization of Ce3+ and La3+. Nitric acid was the more efficient leaching agent for the first group. In the case of organic acids, lactic acid solubilized Ce3+, while mixtures of lactic and citric acids appeared to solubilize La3+.