We investigate alternative focusing geometries to couple near-resonant light onto a single neutral atom. In particular, we show significant light-atom interaction using the ‘4Pi-microscopy’ configuration. Performing a transmission experiment, we find a resonant extinction of 36.6(3)%. Furthermore, photon anti-bunching in the second-order correlation function of the transmitted light demonstrates nonlinear light-atom interaction at the level of single photons. Our results indicate that free-space focusing provides an alternative route to realise nonlinear optics with single photons.