Pararosaniline, an aqueous saturated solution with a concentration of about 0.3%, is a synthetic basic dye used in histology and microscopy. It binds to acidic structures, especially nucleic acids and proteins, and stains them intensely red.

Parararosaniline finds application in various staining methods and is a component of some staining solutions, such as the Ziehl-Neelsen stain, which is used to identify acid-fast bacteria, such as mycobacteria. In histology, pararosanilin can be used to selectively stain and visualize specific cellular structures, such as nuclei, and tissue components, such as elastic fibers or mast cell granules.