The testimony of peace (a.k.a. testimony for peace or testimony against war) is the action generally taken by members of the Religious Society of Friends (Quakers) for peace and against participation in war. Like other Quaker testimonies, it is not a "belief", but a description of committed actions, in this case to promote peace, and refrain from and actively oppose participation in war. Quakers' original refusal to bear arms has been broadened to embrace protests and demonstrations in opposition to government policies of war and confrontations with others who bear arms, whatever the reason, in the support of peace and active nonviolence. Due to this core testimony, the Religious Society of Friends is considered one of the traditional peace churches.

Friends' testimony of peace is largely derived from beliefs arising from the teachings of Jesus to love one's enemies and Friends' belief in the inner light. Quakers believe that nonviolent confrontation of evil and peaceful reconciliation are always superior to violent measures. The testimony of peace does not mean that Quakers engage only in passive resignation; in fact, they often practice passionate activism.

The testimony of peace is probably the best known testimony of Friends. The belief that violence is wrong has persisted to this day, and many conscientious objectors, advocates of non-violence and anti-war activists are Friends. Due to their testimony of peace, Friends are considered one of the historic peace churches. In 1947 Friends as a worldwide religious group were awarded the Nobel Peace Prize, which was accepted by the American Friends Service Committee and the then London Yearly Meeting's Friends Service Committee, now called Britain Yearly Meeting Peace & Social Witness on behalf of all Friends. The testimony of peace has not always been well received in the world; on many occasions Friends have been imprisoned for refusing to serve in military activities.

Some Friends today regard the testimony of peace in even a broader sense, refusing to pay the portion of the income tax that goes to fund the military. Yearly Meetings in the United States, Britain and other parts of the world endorse and support these Friends' actions. The Quaker Council for European Affairs campaigns in the European Parliament for the right of conscientious objectors in Europe not to be made to pay for the military. Some do pay the money into peace charities and still get goods seized by bailiffs or money taken from their bank accounts.

In the United States, others pay into an escrow account in the name of the Internal Revenue Service, which the IRS can only access if they give an assurance that the money will only be used for peaceful purposes. Some Yearly meetings in the US run escrow accounts for conscientious objectors, both within and outside the Society.

Many Friends engage in various non-governmental organizations such as Christian Peacemaker Teams serving in some of the most violent areas of the world. Quaker author Howard Brinton, for example, served in the American Friends Service Committee during World War I.

George Fox, perhaps the most influential early Quaker, made a declaration in 1651 that many see as the first declaration of Friends' beliefs on peace:

Following the 1660 Restoration of King Charles II and a clamp-down on religious radical groups such as the Fifth Monarchists,