Software from Sun that converts a program in Java bytecode (intermediate language) into machine language and executes it. The Java Virtual Machine (JVM) is the runtime engine of the Java Platform, which allows any program written in Java or other language compiled into Java bytecode to run on any computer that has a native JVM. JVMs run in both clients and servers, and the Web browser can activate the JVM when it encounters a Java applet.

The JVM includes a just-in-time (JIT) compiler that converts the bytecode into machine language so that it runs as fast as a native executable. The compiled program can be cached in the computer for reuse.

Microsoft had its own Java Virtual Machine (JVM) for several years, but terminated its support at the end of 2007. See Java, Java Runtime Environment, bytecode and intermediate language.