An enormous research effort is currently being directed towards the development of efficient visible‐light‐driven photocatalysts for renewable energy applications including water splitting, CO2 reduction and alcohol photoreforming. Layered double hydroxide (LDH)‐based photocatalysts have emerged as one of the most promising candidates to replace TiO2‐based photocatalysts for these reactions, owing to their unique layered structure, compositional flexibility, controllable particle size, low manufacturing cost and ease of synthesis. By introducing defects into LDH materials through the control of their size to the nanoscale, the atomic structure, surface defect concentration, and electronic and optical characteristics of LDH materials can be strategically engineered for particular applications. Furthermore, through the use of advanced characterization techniques such as X‐ray absorption fine structure, positron annihilation spectrometry, X‐ray photoelectron spectroscopy, electron spin resonance, density‐functional theory calculations, and photocatalytic tests, structure‐activity relationships can be established and used in the rational design of high‐performance LDH‐based photocatalysts for efficient solar energy capture. LDHs thus represent a versatile platform for semiconductor photocatalyst development with application potential across the energy sector. Nanostructured layered double hydroxide (LDH) photocatalysts, owing to their unique layered structure, compositional flexibility, low cost and ease‐of‐synthesis represent one of the hottest new research directions in semiconductor photocatalysis and solar energy conversion. Structure‐activity relationships in nanostructured LDH compounds are explored, and the importance of using advanced characterization techniques in the future development of more efficient LDH‐based photocatalysts is emphasized.