It's been a long time since I write any Java Error or Exception troubleshooting tutorial so here we are. In this post, we will take a look at the "java.lang.OutOfMemoryError: unable to create new native thread" error which is a rate but quite possible in multithreading Java applications. This is another Java OutOfMemoryError that comes when JVM hits the native thread limitation allowed to be open by one process and not able to create any more new threads. Since each Java thread is associated with the OS thread, when OS refuses to provide a new thread, JVM throws OutOfMemoryError. It's rarely you will see common Java applications throwing this error but it's common when multiple application is using the same Java process e.g. WebServer Tomcat and a significant number of threads are allocated due to high load.