VirtualBox is not available for Android but there are some alternatives with similar functionality. The best Android alternative is KVM (Kernel-based Virtual Machine), which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to VirtualBox and five of them are available for Android so hopefully you can find a suitable replacement. Other interesting Android alternatives to VirtualBox are Proxmox Virtual Environment (Freemium, Open Source), bochs (Free, Open Source), GNURoot Debian (Free, Open Source) and JPCSIM (Free).
KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, kvm.
Almost everyone thinks KVM (Kernel-based Virtual Machine) is a great alternative to VirtualBox.
GNURoot Debian provides a method for you to install and use Debian and its associated applications/packages alongside Android. This does NOT require root. A regular uninstall fully cleans up after this application.