This paper reports R-matrix calculations of electron impact excitation rates for Ni III. The calculation includes 70 LS terms corresponding to the configurations 3d^8^, 3d^7^4s, 3d^7^4p, and 3d^6^4s^2^. This expansion results in 162 fine structure levels and 13041 transitions, including optical, infrared, and ultraviolet lines. The collision strengths, including detailed resonance structures, were integrated over a Maxwellian distribution of electron energies and the resulting effective collision strengths are given for a wide range of temperatures. A collisional-radiative equilibrium model of the Ni III ion is constructed and the strongest lines in the optical and infrared spectral regions are identified. The emissivities of these lines and emissivity line ratio diagnostics are presented.