Terminal lucidity (also known as rallying, terminal rally, the rally, end-of-life-experience, energy surge, the surge, or pre-mortem surge) is an unexpected return of consciousness, mental clarity, or memory shortly before death in individuals with severe psychiatric or neurological disorders. It has been reported by physicians since the 19th century. Terminal lucidity is a narrower term than the phenomenon paradoxical lucidity where return of mental clarity can occur anytime (not just before death). Terminal lucidity is not considered a medical term and there is no official consensus on the identifying characteristics.

Terminal lucidity is a poorly understood phenomenon in the context of medical and psychological research, and there is no consensus on what the underlying mechanisms are. It can occur even in cases of severe, irreversible damage or degeneration to the brain, making its existence a challenge to the irreversibility paradigm of degenerative dementias.

Studying terminal lucidity presents ethical challenges due to the need for informed consent. Care providers also face ethical challenges of whether to provide deep sedation, which might limit terminal lucidity, and how to respond to requests for a change in care plans from family members.

Several case reports in the 19th century described the unusual condition of an improvement and recovery of the mental state in people days or weeks before death. In 1887, William Munk called the phenomenon "lightening up before death".

According to historical reviews headed by the biologist Michael Nahm, the phenomenon has been noted in individuals with diseases which cause progressive cognitive impairment, such as Alzheimer's disease, but also schizophrenia, tumors, strokes, meningitis, and Parkinson's disease. This makes terminal lucidity a phenomenon that is difficult to classify. Researchers are unclear if the phenomenon occurs in all people regardless of their medical history. In 2018, a group of researchers at Dongguk University Ilsan Hospital published a study involving the observation of people weeks prior to death. Out of 151 deaths, six people experienced terminal lucidity. These six had different admission causes, and upon admission three of them were alert and aware and the other three were drowsy. The most common causes of death among these people were different infectious diseases or cancer complications. A survey of 45 Canadian palliative care volunteers reported that 33% of them personally witnessed at least one case of terminal lucidity within the previous year.

According to Nahm, it may be present even in cases of people with previous mental disability. Nahm defines two subtypes: one that comes gradually (a week before death), and another that comes rapidly (hours before death), with the former occurring more often than the latter. There are many cases reported in literature, although the phrase 'terminal lucidity' was coined in 2009. Although interest in this condition dwindled during the 20th century, further studies have re-examined it.

Terminal lucidity is characterized by a transient reversal in an individual's physical symptoms of disease such as Alzheimer's and other similar dementias. This often takes the form in sudden, unexpected, and short-term mental clarity in patients with late-stage memory disorders. For example, those who were previously non-verbal or may have limited communication abilities may regain their ability to speak. Those who experience terminal lucidity may also experience sudden recollection and recognition of people they had previously lost the ability to identify.

During terminal lucidity, cognitive and memory abilities function differently than those of unaffected individuals.