β-receptor blockers or β-adrenoceptor antagonists bind to β receptors and inhibit catecholamine-mediated sympathetic responses. All β blockers are competitive antagonists but differ in characteristics such as adrenoceptor subtype affinity, lipophilicity, and α-blockade ability. β blockers are categorized as either nonselective or selective. The first β blocker was dichloroisoprenaline with partial agonist activity. Further research led to the development of propranolol, which was a pure antagonist but nonselective agent. Next, propranolol analogs were further explored to obtain clinically effective drugs with β1-selectivity. For instance, practolol and atenolol are β1-selective. Few selective β1 antagonists, like metoprolol, showed cardioselective actions. Additionally, β blockers are also categorized generation-wise. The first generation includes older, nonselective molecules, while the second comprises cardioselective molecules. The third generation includes newer drugs such as labetalol and carvedilol with additional α blocking or vasodilatory action. These drugs are therapeutically important in treating heart ailments and hemodynamic disorders.