CuI-based p-type semiconducting and transparent oxide materials have recently gained renewed interest for potential applications in energy-related devices. As a counter-part of n-type transparent oxides like ZnO, SnO2, Indium tin oxide etc., development of p-type transparent conducting oxides has provided a new dimension to the field of 'Transparent Electronics' for new-generation energy-efficient optoelectronic devices. An all-transparent p- n junction device can lead to the formation of a 'functional window' that would transmit the visible light yet generates electricity by the absorption of ultra-violet part. In this article, a comprehensive review on the recent developments and trends on CuI-based p-type oxide material is presented. The origin of visible transparency and p-type conductivity within these types of oxides are discussed. The properties, defect mechanisms and syntheses of various CuI-based p-type oxides, including the parent compound, Cu2O are discussed in details. Also, the applications of various CuI-based p-type oxides in energy-related fields and optoelectronic devices are discussed comprehensively. Finally, the future trend of the CuI-based p-type transparent conducting oxides in terms of syntheses and applications are proposed for potential usage in diverse fields and novel devices.