Breeding and housing wild animals in captive environments can pose challenges for their welfare. In South Africa, thousands of lions (Panthera leo) are bred and raised at commercial captive breeding facilities, so called ‘lion farms’, for use in tourism, trophy hunting and traditional medicine. To gain a better understanding of the potential welfare challenges faced by lions on farms we reviewed 91 peer-reviewed articles relating to lion welfare, identified via a systematic review of the scientific literature. Across these studies, we identified 170 different terms relating to negative behaviours and physical health afflictions. The majority of these terms were associated with disease and injury (124; 73%), followed by negative behaviours (19; 11%), negative mental experiences (15; 9%), nutritional concerns (7; 4%), and environmental challenges or discomfort arising from the animal's surroundings (5; 3%). Of the 91 articles, 32 (35%) focused on data concerning captive lions. Only two studies focused specifically on data obtained from lion farms in South Africa, whilst the remainder reported on data collected from zoos, wildlife parks, sanctuaries, game reserves and private ownership. Our preliminary review of the scientific literature draws attention to some of the challenges associated with caring for lions in captivity, and outlines the potential significance of these welfare challenges for commercial lion farms. Our data highlight the apparent lack of scientific research involving captive lion welfare generally, particularly data collected at commercial breeding facilities in South Africa and the consequences this could have for the welfare of thousands of lions within the industry.