This chapter presents feedback cooling of all translational degrees of freedom of a neutral nanoparticle levitated in a one-dimensional optical lattice near the quantum ground state. This technique is important as it enables the generation of a nearly pure quantum state that is decoupled from the electrical environment. Feedback cooling to the quantum ground state has so far been demonstrated only for charged nanoparticles using electrical cold damping. However, this technique is inapplicable to electrically neutral particles, as they do not respond to electric fields. Cooling neutral particles is important for Time-of-Flight measurements described in Chapter 6, since their motion is not disturbed by stray electric fields in the vacuum chamber. To achieve ground state cooling, we carefully suppress environmental heating sources. We experimentally evaluate environmental heating and confirm that photon recoil from the trapping laser is the dominant source. As a result, we demonstrate full feedback cooling of all three translational degrees of freedom. Notably, motion along the optical lattice axis is cooled to the occupation number \(<{n}>=0.69\pm 0.18\) , indicating the ground state.