The radiation environment beyond Low Earth Orbit (LEO) presents the major isolated challenge to the human exploration of the Solar System. Additionally, it is also an hazard to spaceship and satellite instruments and systems and it has to be taken into account in the planning of any mission that is sent to space. The radiation environment in Space is constituted by the Galactic Cosmic Rays; the occasional, but very intense Solar Energetic Particle Events; the Solar Wind particles, and the planetary radiation belts. The latter are mostly constituted by electrons and protons captured by the magnetospheres of iron core planets. Spaceship systems and instruments for any space mission are designed taking into account the radiation environment expected for the full mission span, which may vary depending on the epoch and on the trajectory of the mission. When measurements of the radiation environment are scarce or not available, radiation environment models are fundamental to the development of mitigation strategies for radiation damage. Space radiation environment models can be complex, because of the different factors that have to be taken into account, such as solar cycle conditions, the existence and strucure of planetary magnetospheres, the composition of the planetary atmospheres and surfaces and the local topography. On the other hand, measuring the radiation environment in space and in planetary environments, also requires predictions from the models, which are fundamental in the tailoring and in the optimization of radiation detectors that can achieve the best possible performance for the unique measurement opportunities presented by spatial missions.