pacifist
n.someone who believes that war and violence are always wrong. A person like this refuses to fight or use force to solve problems.
n.a person who holds the belief that war and violence are unjustifiable and that all disputes should be settled by peaceful means.
“He is a lifelong pacifist who refuses to join the army.”
“During the conflict, many pacifists were imprisoned for refusing to participate in the mandatory military draft.”
“The philosopher's transition from a soldier to a committed pacifist was driven by his firsthand experience of the devastation wrought by modern industrial warfare.”
Can also be used as an adjective to describe beliefs or actions that support peace.
From French pacifiste, equivalent to pacific + -ist.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.