http://mdpi.com/journal/sensors/special_issues/space_sensors/ The rapid growth and implementation of photonic devices in both civil and military systems have reached the stage of applications of the technology in the space. Photonics has many already perceived benefits for applications in space, such us small size, light weight, high resolution, electromagnetic interference immunity, capability of operating in harsh environment, multiplexing capability, potentially low cost. Among photonic devices, sensors have been extensively studied in the last decades for different application fields, with different geometrical configurations, materials and detection schemes, resulting in a large number of designs and a wide range of performance. Specific requirements from the space application field is pushing the development of new photonic sensors to be used on-board, e.g. for structural monitoring of space vehicles, for detection of chemical and biological substances, for high resolution inertial systems, also integrating the sensing systems to the optical communication networks with consequent advantage of using the optical transmission circuits as monitoring ad diagnostic media. This special issue focuses on photonic sensors for space applications, with the aim of providing research advances on the potential of the sensors to the space field.