Methods and apparatus, including computer systems and program products, for sharing classes and class loaders. One implementation provides a technique for performing a shared load procedure for a class, performing a post load procedure for the class, performing a shared link procedure for the class, performing a post link procedure for the class, and performing an initialization procedure for the class to reduce memory consumption and class loading time. Through performance of these procedures, a first portion of the class (which may include a class block and object) is loaded into a shared memory accessible by multiple runtime systems, and a second portion of the class (which may include a class static variable) as is stored in a local memory associated with a selected runtime system. A shared master copy of the second portion of the class is also stored in the shared memory.