Amnesia (; ), also known as amnesic syndrome, is a deficit in memory caused by brain damage, disease, or psychological trauma. Amnesia can also be caused temporarily by the use of various sedatives and hypnotic drugs. Essentially, amnesia is loss of memory. The memory can be either wholly or partially lost due to the extent of damage that was caused. There are two main types of amnesia: retrograde amnesia and anterograde amnesia. Retrograde amnesia is the inability to retrieve information that was acquired before a particular date, usually the date of an accident or operation. In some cases the memory loss can extend back decades, while in others the person may lose only a few months of memory. Anterograde amnesia is the inability to transfer new information from the short-term store into the long-term store. People with this type of amnesia cannot remember things for long periods of time. These two types are not mutually exclusive. Both can occur within a patient at one time. Case studies, such as that of patient R.B., show that both types of amnesia can occur simultaneously. Case studies also show that amnesia is typically associated with damage to the medial temporal lobe. In addition, specific areas of the hippocampus (the CA1 region) are involved with memory. Research has also shown that when areas of the diencephalon are damaged, amnesia can occur. Recent studies have shown a correlation between deficiency of RbAp48 protein and memory loss. Scientists were able to find that mice with damaged memory have a lower level of RbAp48 protein compared to normal, healthy mice. In people suffering with amnesia, the ability to recall immediate information is still retained, and they may still be able to form new memories. However, a severe reduction in the ability to learn new material and retrieve old information can be observed. Patients can learn new procedural knowledge. In addition, priming (both perceptual and conceptual) can assist amnesiacs in the learning of fresh non-declarative knowledge. Amnesic patients also retain substantial intellectual, linguistic, and social skill despite profound impairments in the ability to recall specific information encountered in prior learning episodes.

is a Japanese visual novel series by Idea Factory. It was first released on August 18, 2011 for PlayStation Portable, and then a fan disc in Japan, Amnesia Later, was released on March 15, 2012. Another sequel titled Amnesia Crowd was released on April 18, 2013. They were later combined for a PlayStation Vita release titled "Amnesia Later x Crowd V Edition" on October 16, 2014. Since this series is well received in Japan, it produced various related merchandise such as drama CDs, character music CDs and books. A 2013 anime television series has been produced by Brain's Base. A PlayStation Vita game has been announced.

Amnèsia is an Italian comedy-drama film directed by Gabriele Salvatores and released in 2002.