The particle nature of neutrinos is one of the most fundamental open questions in physics today. It is possible that neutrinos are Majorana in nature, i.e. single particles that represent both matter and anti-matter states. The implications of Majorana neutrinos would be far-reaching: it would demonstrate that lepton number is not conserved, point to the existence of heavy neutrinos at a new mass scale, and be a key ingredient to understanding the origin of the matter-antimatter asymmetry in the universe today.

The most promising approach to experimentally verifying the possible Majorana nature of neutrinos comes from searching for rare double beta decays in which no neutrinos are emitted. In this talk I will describe the nEXO experiment, a proposed tonne-scale search for the neutrinoless double beta decay (NLDBD) of 136Xe. nEXO will build on the previous EXO-200 detector design and make full use of the self-shielding capabilities of a large, monolithic, liquid xenon detector to extend our current sensitivity to NLDBD by nearly two orders of magnitude. This talk will give an overview of the design and science goals of nEXO, highlighting the importance of reducing radioactive backgrounds in order to attain world-leading sensitivity.