The Microsoft Java Virtual Machine (MSJVM) is a discontinued proprietary Java virtual machine from Microsoft. It was first made available for Internet Explorer 3 so that users could run Java applets when browsing on the World Wide Web. It was the fastest Windows-based implementation of a Java virtual machine for the first two years after its release. Sun Microsystems, the creator of Java, sued Microsoft in October 1997 for incompletely implementing the Java 1.1 standard. In 2001, Microsoft settled the lawsuit with Sun and discontinued its Java implementation.

The initial release of Windows XP in 2001 did not ship with a Java virtual machine, because of the settlement with Sun.

The Microsoft Java Virtual Machine was discontinued in 2003 in response to the Sun Microsystems lawsuit. Microsoft continued to offer support until December 31, 2007.