The geochemical characterization of Himalayan leucogranites offers important insights into both their petrogenesis and Himalayan orogenic processes. Himalayan leucogranites are characterized by strongly peraluminous compositions that are comparable to melts derived from anatexis of sedimentary rocks. Their radiogenic (Sr, Nd, and Hf) isotopic compositions point to metasediments from the Higher Himalayan Sequence of the Indian plate as the primary source rocks, with minor contributions from other lithologies. Himalayan leucogranites display considerable variability in trace element ratios (e.g., Rb/Sr, Nb/Ta, Zr/Hf, and Eu/Eu*) and significant fractionation of non-traditional stable isotopes (e.g., Mg, K, Zn, Rb, and Ba), which provide key constraints on the respective roles of source heterogeneity, crystal fractionation, magma–fluid interaction, and crustal melting in their formation.