Aeterna Dei sapientia ("God's eternal wisdom") was the sixth encyclical made by Pope John XXIII, and was issued on 11 November 1961.

It calls for Christendom to unite against external movements such as communism and secularism.

John then puts Leo's papacy in the context of the upcoming Second Vatican Council.

He then mentions the doctrine of the infallibility of the church promulgated by his predecessor, Pope Pius IX, and discusses the development of the modern understanding of the papacy.

After more discussion of the Magisterium and the council, John concludes by acknowledging the division present in the church, invoking Pope Leo, and once more calling for unity.