ackground: Food insecurity (FI) is a multifaceted, socioeconomic problem involving difficulties accessing sufficient, safe and nutritious food to meet people’s dietary requirements and preferences for a healthy life. For children experiencing FI, there are some potentially negative developmental consequences and it is, therefore, important to understand the links between FI and children’s health and well-being as well as any strategies undertaken to address FI. The overall objective of this assessment was to determine the nature, extent and consequences of FI affecting children (aged ≤ 18 years) in the UK. Objective: To determine the nature, extent and consequences of FI affecting children (aged ≤ 18 years) in the UK. Data sources: The databases searched on 4 December 2017 included MEDLINE (including In-Process & Other Non-Indexed Citations and E-pub ahead of print files), EMBASE, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Commonwealth Agricultural Bureaux (CAB) abstracts, The Cochrane Library, Education Resources Information Centre (ERIC), PsycINFO, the Social Science Citation Index and the Applied Social Sciences Index and Abstracts (ASSIA). Methods: A rapid review of the current published and unpublished literature was conducted, including all study designs from specified high-income countries in children aged ≤ 18 years. Searches were conducted of major health-care, nutrition, education and social science databases from 1995 onwards, and websites of relevant UK and international organisations. Final searches were undertaken in December 2017. Results: In total, 109 studies were selected. Only five studies were conducted in the UK, four of which provided qualitative data. Possible factors associated with child FI were identified, for example socioeconomic status, material deprivation, living in public housing and having unemployed or poorly educated parents. Children’s health, well-being and academic outcomes were all negatively affected by FI. The mediating effects of family stressors and parenting practices in the relationship between FI and children’s health and well-being outcomes were not clear. Food assistance programmes were generally effective in mitigating FI and improving nutritional outcomes (including hunger) in the short term, but did not eradicate FI, eliminate its effects on children’s health or have an impact on academic outcomes. No reports assessing the prevalence of child FI in the UK or the cost-effectiveness and sustainability of interventions to tackle FI were identified. Limitations: There was a lack of consistency in how FI was defined and measured across studies. Most of the studies used indirect measurements of child FI through parental reports. The majority of studies were conducted in North America. Only five studies were conducted in the UK. Thirty potentially relevant studies were not included in the review as a result of time and resource constraints. Most studies were observational and caution is advised in interpreting their results. Conclusions: A number of factors that were related to child FI were identified, as were negative associations between child FI and physical, mental and social outcomes. However, these findings should be interpreted with caution because of the correlational nature of the analyses and the fact that it is difficult to determine if some factors are predictors or consequences of FI. Future research: There is an urgent requirement for the development of a reliable instrument to measure and monitor child FI in the UK and for well-designed interventions or programmes to tackle child FI. Study registration: This study is registered as PROSPERO CRD42017084818. Funding: The National Institute for Health Research Public Health Research programme. The Health Services Research Unit is core-funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates.