A golf ball marking stencil includes two caps, resiliently biased toward one another, configured as spherical segments defining a cavity therebetween to securely retain a golf ball. Stencil slots for marking putt alignment path, putter face squareness and swing path lines are defined in the caps. Actuator tabs project from the caps and may be pinched together in opposition to a bias spring to force the caps open to expose the cavity. The spring force of the bias spring prevents movement of a retained golf ball relative to the caps. The cavity periphery is contoured to permit a marker pen to be engaged therein when the cavity does not contain a golf ball.