A laser collimator is a narrow-field imaging system that is designed for near-diffraction-limited performance when operating at a single wavelength. Although a traditional design might consist of a homogeneous doublet, the design of an axial gradient-index (GRIN) singlet for such an application is described. The analysis begins with third-order aberration thin lens optical design principles in order to examine the effects of spherochromatism from the GRIN. The final design is optimized in CODE V® using GRIN aluminum oxynitride (ALON®), which allows for diffraction-limited operation from the visible through 5 μm. A tolerance analysis is performed on the slope, nonlinearity, and tilt of the GRIN profile in order to assess sensitivity to fabrication errors.