Chief Rabbi Lord Sacks and Pope Benedict XVI discussed their mutual fears for Europe's future during an audience at the Vatican.
The meeting came as the Chief Rabbi made a two-day visit to Rome and the Holy See.
The religious leaders discussed the role of faith and morality and their hopes for a regeneration of Europe, both economically and socially.
Pope Benedict was presented with a copy of the Koren Sacks Siddur by the Chief Rabbi. It was inscribed: "In respect, admiration and brotherly love - may the friendship between us and between our two ancient faiths bring blessing to the world."
The issue of Europe was also addressed as the Chief Rabbi gave a lecture at the Cardinal Bea Centre for Judaic Studies at the Pontifical Gregorian University.
He called on Christians and Jews to open a "new chapter" in their relationship: "If Europe loses the Judeo-Christian heritage that gave it its historic identity and its greatest achievements in literature, art, music, education, politics, and economics, it will lose its identity and its greatness.
"When a civilisation loses its faith, it loses its future. When it recovers its faith, it recovers its future. For the sake of our children … we - Jews and Christians, side-by-side - must renew our faith and its prophetic voice. We must help Europe rediscover its soul."
On Sunday, the first day of his visit, the Chief Rabbi was guest of honour at a reception for the Italian Jewish community at the Great Synagogue of Rome. Among the 200 dignitaries was Riccardo Di Segni, Chief Rabbi of Italy.