Is the OOM Killer active in Linux when there is no SWAP partition?

Yes, the OOM Killer in Linux is active even when there is no SWAP partition. SWAP is an additional area on the disk used to extend available virtual memory, but its absence does not disable the OOM Killer mechanism. When the system runs out of available RAM and SWAP, the Linux kernel activates the OOM Killer to terminate processes and free up memory, preventing system hang.