Beta blockers (short for beta-adrenergic blocking agents) are drugs that interfere with or "block" the function of certain neurotransmitters in the brain, such as norepinephrine and epinephrine (also known as adrenaline).

Normally, the body uses these neurotransmitters to initiate emotional reactions to stress: increased heart rate, increased breathing rate, increased blood flow to muscles. Together, these reactions are called the "fight or flight" response, and they prepare the body to deal with an emergency or threat (typically by fighting or running away).

Beta blockers interfere with this process, and so they can be helpful in curing stage fright, which is an overreaction to a stressful but non-lethal situation, and in treating migraines, which can be triggered by stress.

Because beta blockers lower blood pressure and heartrate in general, they are also sometimes used to treat high blood pressure and some forms of heart disease.