Relaxin family peptide 3 receptor (RXFP3) is a G protein-coupled receptor that is activated by the endogenous peptide ligand, relaxin-3. Relaxin-3/RXFP3 are highly enriched within the brain, and rodent pharmacological studies conducted by us and collaborators have demonstrated that this system can strongly influence feeding behaviour and stress responses. For example, direct brain injection (to circumvent the blood brain barrier) of peptide RXFP3 agonists robustly increases food consumption in rats, while peptide RXFP3 antagonists reduce feeding in mice. Furthermore, brain injection or intranasal delivery of peptide RXFP3 agonists reduces anxiety and depressive-like behaviour in rodents. These findings highlight the promising potential of RXFP3 as a therapeutic target to treat obesity and/or depression. However, the mechanisms within the brain that underlie these roles remain poorly understood, and in particular, the specific neuronal sub-types that express RXFP3 within key feeding and stress-related brain regions remains mostly unknown. To address this gap in knowledge, we have established a transgenic strain of mouse that expresses a fluorophore within RXFP3-positive cells. Using immunohistochemistry, we have revealed that RXFP3 is expressed by dopamine and gonadotropin releasing hormone neurons within key hypothalamic feeding centres. Interestingly, we have also revealed that RXFP3 is expressed by enteric neurons within the gut, suggesting synergistic roles and possible influence on the brain-gut axis. Additionally, RXFP3 is heavily expressed in the amygdala, and approximately half of these neurons also express the opioid peptide enkephalin which strongly influences stress and emotional/behavioural outputs. Taken together, these studies provide important insights into the likely mechanisms through which RXFP3 signalling controls feeding and stress-related behaviours. This work forms the foundation for future studies which will use recently developed RXFP3 agonists and antagonists that cross the blood brain barrier, to observe whether peripheral delivery in mice influences behaviours and neuronal pathways relevant to obesity and depression.