Long fibre-reinforced thermoplastic or long fibre thermoplastic (LFT) composites possess superior specific modulus and strength, excellent impact resistance, and other advantages such as ease of processability, recyclability, and excellent corrosion resistance. These advantages make LFT composites one of the most advanced lightweight engineering materials and enable their increasing use in various applications. This review paper summarises the research and development work that has been conducted on LFT composites since their initial development. Different aspects of LFTs, such as process development, fibre orientation distribution (FOD), fibre length distribution (FLD), and their effects on the mechanical properties of LFT composites are described. The characterisation of the FOD and FLD in the LFT composites using advanced imaging technology such as high-resolution 3D micro-CT scanning technique is summarised. Research and development of LFT hybridisation and LFT additives are also discussed. Finally, conclusions are made and the future outlook of LFT composites is given.