Liquid-liquid extraction is one of the most important techniques for the separation of rare earth metals in hydrometallurgy. Recently, ionic liquids (ILs) have attracted much attention as green alternatives to conventional organic solvents. Due to the additional advantage of good radiation stability, their application to the separation of fission products in nuclear fuel reprocessing has been promoted. In this article, we summarize the IL-based extraction of rare earth metals and advanced techniques are described.