Terbutaline, sold under the brand names Bricanyl and Marex among others, is a β2 adrenergic receptor agonist, used as a "reliever" inhaler in the management of asthma symptoms and as a tocolytic (anti-contraction medication) to delay preterm labor for up to 48 hours.

This time can then be used to administer steroid injections to the mother which help fetal lung maturity and reduce complications of prematurity.

Since there is no hydroxy group on position 4 of the benzene ring, the molecule is less susceptible to metabolism by the enzyme catechol-O-methyl transferase.

This is a racemate, ie a 1: 1 mixture of (R) - and the (S) - form:[15] As with all β2-adrenergic receptor agonists, terbutaline is on the World Anti-Doping Agency's list of prohibited drugs, except when administered by inhalation and a Therapeutic Use Exemption (TUE) has been obtained in advance.

Brand names include Astherin, Bronclyn, Brethine, Bricanyl, Brethaire, Marex, Terasma, and Terbulin.