A Memory Charm (also known as the Forgetfulness Charm) is a spell that can be used to erase memories from an individual's mind. The incantation for this charm is Obliviate. It is different from the charm that creates false memories.
Memory Charms are generally intended to erase a specific memory. They are regularly used if a Muggle witnesses something related to the wizarding world; the Ministry of Magic has Obliviators remove their memories of the event, such as if a Muggle sees a dragon. Occasionally, a mass use of Memory Charms is necessary to cover up major incidents that violate the Statute of Secrecy. Some Muggles often slip through the cracks in these situations, according to Blenheim Stalk in Muggles Who Notice. When particularly intense memories need to be erased, it often leaves the victim disoriented for a short period of time.
However, if performed improperly, a Memory Charm can erase significant portions of an individual's memory and cause brain damage, with difficulty in recovery. For instance, Professor Gilderoy Lockhart attempted to use the spell on both Harry Potter and Ron Weasley during the events surrounding the re-opening of the Chamber of Secrets. However, Ron's damaged wand backfired, and caused Lockhart to suffer extreme amnesia. He is currently a permanent resident in the Janus Thickey Ward of St Mungo's. Despite his memories recovered enough to do joined-up writings and his love of signing fan letters, he never fully recovered.