Ground bean (Macrotyloma geocarpa) is an underutilized legume with strong potential to address soil fertility decline and food insecurity in smallholder farming systems worldwide. Climate variability, low soil nitrogen, and reliance on a few staple crops limit sustainable food production in rainfed and marginal environments. This highlights the need for climate-resilient, low-input legumes that enhance both soil health and household nutrition. This chapter aims to synthesize agronomic, nutritional, and socio-ecological evidence on the role of ground bean in improving soil fertility and food security. It integrates botanical and agronomic characterization, climate adaptation strategies, nutritional analyses, crop modelling, and documented case studies from major production regions. Case studies showed grain yields ranging from 0.6–1.2 t ha−1 under rainfed conditions. Soil nitrogen increased by 15–20% through biological nitrogen fixation. Household nutrition studies reported daily protein contributions of 18–22 g per capita from ground bean consumption. Processing interventions increased seed protein content by 12% and reduced phytic acid by 35%, improving mineral bioavailability. These findings confirm the dual role of ground bean in soil fertility restoration and nutrition security. Future efforts should focus on breeding stress-tolerant genotypes. They should also improve rhizobial inoculation, strengthen value chains, and integrate ground bean into climate-smart agricultural policies.