ViennaMaterials is a free open-source library written in C++ for hosting material parameters which is particularily relevant for scientific simulations. Material data are stored in XML files, which are processed and hosted by ViennaMaterials via its API. The API enables external tools (e.g. simulators) to query material data and use the query results to feed the simulation facilities. A unit conversion mechanism ensures that material parameters are accessed in a unit-agnostic manner. The library is currently under development and hosted on github using a MIT/X11 license.