FMRP, or Fragile X Mental Retardation Protein, is a multifunctional RNA-binding protein that plays a crucial role in synaptic development and plasticity in the nervous system. It is widely expressed across all tissues, although at varying levels, and is not restricted to the synapse or neurons. It is involved in regulating the fate of stem cells, being essential for stem cell maintenance and inhibiting stem cell differentiation. FMRP binds to a variety of RNAs, including methylated histone, ribosome, mRNP, and other proteins. It is known to interact with a specific set of mRNAs, aiding in their transport along microtubules and regulating their translation through association with ribosomes. FMRP is established as a translation repressor, but recent studies on mouse and human FXS models suggest that FMRP is involved in regulating almost all aspects of gene expression. It can also enhance the translation of its target mRNAs by binding to the coding sequence and hindering ribosome movement on mRNA. FMRP deficiency is associated with Fragile X Syndrome (FXS), the most common inherited cause of intellectual disability and autism. FMRP has also been implicated in cancer growth and immune evasion.