ABSTRACT The request for packaging technologies which enable electronic devices to operate under harsh environments is always increasing. The main challenge is the encapsulation of electronic circuits to save them from external thermal influences and to resist fast thermal gradients. Other aspects of harsh environments are radioactive, chemical, electromagnetic and high-pressure surroundings. For all of these special influences, different embodiments for the packaging must be chosen. For example, for industrial applications ceramic is often used to ensure a long-term stability of about 10 years. This chapter gives an overview of the different techniques for the fabrication of packages for operation under harsh environments.