This book on "Optical phase conjugation studies in dye-doped gelatin films" is written for the benefit of peoples who are interested in the field of nonlinear optics and materials. The first chapter starts with introduction to nonlinear optics, optical phase conjugation and Z-scan measurements of third-order nonlinear optical properties of materials. A detailed study of literatures have also been presented at the end of this chapter. The second chapter includes the experimental study of optical phase conjugation in triphenylmethane dye-doped gelatin films using a 633 nm He-Ne laser with 35 mW of total power. The third chapter presents the Z-scan measurements of third-order optical nonlinearities of triphenylmethane dyes. The fourth chapter deals with demonstration of phase conjugate interferometry in the triphenylmethane dye-doped gelatin films. The fifth chapter concludes the overall experimental results, discussions and suggests for the future direction of studies in the field of optical phase conjugation.