Luminescent materials are substances that emit light when stimulated by external energy sources. This chapter explores the applications of luminescent materials in optical thermometry, pH sensing, and forensic analysis. Optical thermometry using luminescent materials offers remote temperature measurement capabilities with high sensitivity. The technique relies on temperature-dependent luminescence features, such as luminescence intensity ratio, excited-state lifetime, and spectral shifts. It is possible to map temperatures accurately in various settings, from biological systems to industrial processes, by calibrating the luminescent properties based on known temperature fluctuations. The pH sensing is another significant application of luminescent materials, particularly in biomedical and environmental monitoring. pH-sensitive fluorophores exhibit changes in luminescence intensity or emission wavelength in response to variations in pH levels. Such dependency enables accurate and real-time pH measurements in aqueous solutions or biological samples. Luminescent pH sensors have advantages like quick response, high sensitivity, and compatibility, making them valuable tools for diverse analytical applications. Certain luminous compounds show selective interactions with particular analytes enabling high sensitivity and selectivity in detecting latent fingerprints, bloodstains, or chemical residues for forensic applications. Moreover, targeted imaging and the identification of biomolecules or poisons in samples can be improved through the functionalization of luminous nanoparticles. Further study of known materials and the creation of new luminescent materials are essential for such cutting-edge sensing and imaging technologies.