L-theanine, also known as L-γ-glutamylethylamide and N⁵-ethyl-L-glutamine, is an amino acid analogue of the proteinogenic amino acids L-glutamate and L-glutamine. It is primarily found in certain plant and fungal species. L-theanine is an amino acid found in tea and some mushrooms, and it comes in two forms: L-theanine and D-theanine, with L-theanine being the most common form. It is said to block the effects of glutamate and might also affect the brain chemicals GABA, dopamine, and serotonin. People use L-theanine to improve mental function, for anxiety, mental impairment, stress, and other conditions, although there is no strong scientific evidence to support these uses. L-theanine is known for helping people relax and has potential health benefits, including anxiety and stress relief. Research suggests that L-theanine might provide a range of health benefits, such as supporting thinking, sleep, relaxation, weight loss, and blood pressure regulation.