Hedonism is the moral theory according to which all and only pleasant and unpleasant states have intrinsic value.
Further reading
Chappell, Richard Y., Darius Meissner & William MacAskill (2022) Hedonism, in ‘Theories of well-being’, An Introduction to Utilitarianism.
Moore, Andrew (2004) Hedonism, Stanford Encyclopedia of Philosophy, April 20 (updated 13 December 2019).