Fluoride (F–) contamination in groundwater has received significant attention in recent decades owing to its toxicity to humans. Although referred as a “double-edged sword”, F– in a lower amount prevents dental caries while an excessive amount of F– induces irreversible dental and skeletal fluorosis and is thus detrimental. Therefore, this study was conducted to investigate sources, health effects and defluoridation techniques in various developing countries where the problem is severe. The study revealed that (1) F– contamination in groundwater is widespread and mostly found in arid and semi-arid regions in developing nations. (2) F– in groundwater is primarily influenced by F–-bearing aquifers, prevailing geological and meteorological conditions, longer rock-water interaction, and ion-exchange reactions. (3) Many developing countries are struggling to meet the F– standards set by the WHO due to lack of knowledge and constraints. The study documents the extent of F– contamination, its potential origins, remedial strategies/defluoridation techniques and various projects/programmes for defluoridation in developing countries. The study emphasizes the need to extent research on more effective and affordable defluoridation methods for both individual households and community water supply systems. Finally, the study also highlights various challenges and suggests future research paths to address elevated F– concentration in achieving the UN’s sustainable goal of providing safe drinking water.