无穷循环（infinite loop）或称为无限循环，是指程序的控制流程一直在重复运行某一段代码，无法结束的情形，其原因可能是因为程序中的循环没有设结束循环条件，或是结束循环的条件不可能成立等。在合作式多任务（cooperative multitasking）的操作系统中，无穷循环会使系统没有反应，若是先占式（preemptive）多任务的系统中，无穷循环会用掉所有可用的处理器时间，不过可以由使用户结束进程。无穷循环是造成系统假死机的原因之一，其他的可能原因包括死锁或是内存区段错误。

忙碌等待循环是在外界特定条件时（例如有按键输入）才会离开的循环，有时忙碌等待循环也被称为是无穷循环，但此情形和上述的不太一様。忙碌等待循环可以借由外界事件而结束循环，但上述的无穷循环是无法结束的。

An infinite loop (or endless loop) is a sequence of instructions in a computer program which loops endlessly, either due to the loop having no terminating condition, having one that can never be met, or one that causes the loop to start over. In older operating systems with cooperative multitasking, infinite loops normally caused the entire system to become unresponsive. With the now-prevalent preemptive multitasking model, infinite loops usually cause the program to consume all available processor time, but can usually be terminated by the user. Busy wait loops are also sometimes called "infinite loops". One possible cause of a computer "freezing" is an infinite loop; others include thrashing, deadlock, and access violations.