Tacrine is a drug used for treatment of symptoms associated with Alzheimer's disease. It was approved by the US Food and Drug Administration (FDA) in 1993 and is currently marketed under the brand name of Cognex. Tacrine was the first drug approved to treat Alzheimer's in the US; however, it can cause serious side effects including liver problems, and so its use has declined.

Tacrine works to increase the level of acetylcholine in the brain. Acetylcholine is a neurotransmitter which is important for learning and memory; one feature of AD is a reduction in brain levels of acetylcholine. Like the other currently-available AD drugs, donepezil (trade name Aricept), rivastigmine (trade name Exelon) and galantamine (trade name Reminyl), tacrine is a cholinesterase inhibitor, meaning that it acts to inhibit the enzymes which break down unused acetylcholine; the result is that existing acetylcholine survives longer and is more effective.