Abstract <p>The paper discusses approaches to the legal regulation of thermonuclear fusion at the international and national levels (United Kingdom, USA, China, Canada, Japan, Korea, EU, and Russian Federation). Based on the analysis of the current state of legal regulation of thermonuclear fusion, it is shown that far from all states have established own regulatory framework in this area, and it is also concluded that most of the studied states adhere to (or have declared their intention to) approach aimed at distinguishing fusion from fission technologies. The author noted differences in positions regarding the evolutionary approach, viz., establishing of deterministic requirements to the regulation of thermonuclear fusion as technology develops. The need to harmonize the regulation of fusion at the international level is emphasized, which requires promoting and strengthening international cooperation to develop agreed principles of ensuring universal levels of safety and protection in the field of thermonuclear energy use.</p>