A memory wipe was a medical procedure designed for the purpose of selectively eliminating memory engrams from the mind of an individual.
The neural neutralizer was an early attempt at a device for erasing memories. (TOS: "Dagger of the Mind")
Dr. Katherine Pulaski developed a memory wipe technique which was effective on many humanoid species. It was used on Sarjenka, a young girl from the pre-warp civilization on Drema IV, in order to prevent her from telling her people of her experiences with the Enterprise. (TNG: "Pen Pals")
The technique was not successful on all humanoids, however. Mintakans were unaffected by the memory wipe (TNG: "Who Watches The Watchers"), as were the Boraalans (TNG: "Homeward").
A memory wipe was used by Dr. Julian Bashir to reassign Kurn's identity to Rodek in 2372. (DS9: "Sons of Mogh")
As of 2374 the Ramurans used a neurolytic emitter to erase memories of recaptured refugees. (VOY: "Unforgettable")