Tris(2,2'-bipyridine)nickel(II) chloride is a coordination complex with the chemical formula [Ni(bpy)3]Cl2. It is a paramagnetic, octahedral complex where the nickel(II) center is coordinated by three bidentate 2,2'-bipyridine ligands. This compound typically appears as a purple or violet solid and is soluble in polar solvents such as water and methanol. Its primary applications are in the fields of materials science and catalysis. As a classic electrochemiluminescent (ECL) compound, it serves as a core component or a reference material in the development of light-emitting electrochemical cells (LECs) and other optoelectronic devices. The complex is also investigated as a catalyst or catalyst precursor for various organic transformations, including cross-coupling reactions and photoredox catalysis, leveraging its redox-active nickel center and light-absorbing properties. The compound is sensitive to air and moisture over prolonged periods and should be stored under an inert atmosphere. It is commonly used as a research chemical in academic and industrial laboratories for fundamental studies on charge transfer, photophysics, and catalytic mechanisms involving first-row transition metals.