According to utilitarianism, an action is morally right if it results in the greatest amount of good for the greatest amount of people affected by the action. In other words, the theory states that actions are right if they bring a large number of people happy.
This theory dates back to ancient times. However, it became popular by 18th and 19th-century philosophers who were British. These philosophers include John Stuart Mill, Francis Hutcheson, and Jeremy Bentham. Hutcheson and Bentham would describe the idea, but Mill is the one who named the idea utilitarianism.
According to utilitarianism, an action is morally right if it results in the greatest amount of good for the greatest amount of people affected by the action.