Large Neutrino Flavor Mixings and Lepton Mass Matrices

Recent atmospheric neutrino data at Super-Kamiokande suggest the near-maximal flavor mixing. Models for the lepton mass matrix, which give the near-maximal flavor mixing, are discussed in this report. Mass matrix models are classified according to the mechanism providing the large flavor mixing, and those are reviewed briefly. "Naturalness" of the mass matrix is also discussed in order to select the neutrino mass matrix. Details of the mass matrix with the $S_3$ flavor symmetry are presented.