Walking with a cane, Benedict received another standing ovation from thousands of clerics gathered in the Vatican's main audience hall.
The Vatican has said Benedict would reflect on his personal experiences as a young theological expert attending the Second Vatican Council, the 1962-65 meetings that brought the Catholic Church into the modern world.
Benedict spent much of his 8-year pontificate seeking to correct what he considers the misinterpretation of Vatican II, insisting that it wasn't a revolutionary break from the past, as liberal Catholics paint it, but a renewal and reawakening of the best traditions of the ancient church.
During an emotional final public Mass on Wednesday, Benedict lamented the internal church rivalries that have "defiled the face of the church" a not-too-subtle message to his successor and the cardinals who will elect him.
Those rivalries came to the fore last year with the leaks of internal papal documents by the pope's own butler. The documentation revealed bitter infighting within the highest ranks of the Catholic Church, allegations of corruption and mismanagement of the Holy See's affairs.
Benedict took the scandal as a personal betrayal and a wound on the entire church. In a sign of his desire to get to the bottom of the leaks, he appointed a commission of cardinals to investigate alongside Vatican investigators. His butler, Paolo Gabriele, was convicted and sentenced to 18 months in prison, although Benedict ultimately pardoned him.