L⁴Linux is a variant of the Linux kernel for operating systems, that is altered to the extent that it can run paravirtualized on an L4 microkernel, where the L4Linux kernel runs a service. L4Linux is not a fork but a variant and is binary compatible with the Linux x86 kernel, thus it can replace the Linux kernel of any Linux distribution.

L⁴Linux is being developed by the Dresden Real-Time Operating System Project (DROPS) to allow real-time and time-sharing programs to run on a computer in parallel at the same time.

L⁴Linux also allows setting up a virtualized environment vaguely similar to Xen or Kernel-based Virtual Machine (KVM), but a few significant differences exist^{[further explanation needed]} between the intent of Xen and L⁴Linux.

L4Android^[1] is a fork of L⁴Linux which encompasses the modifications to the main-line Linux kernel for Android. It is a joint project of the operating systems group of the Dresden University of Technology and the chair for Security in Telecommunications of Technische Universität Berlin.

• Wombat (operating system)
• MkLinux, a similar port of the Linux kernel, but to a Mach microkernel