Benedict XVI's reign as pope has come to an end amid the ringing of church bells in Vatican City.
The Swiss Guards went off duty on Thursday at 19:00 GMT after closing the high doors to the papal palace.
From his temporary quarters in Italy's Castel Gandolfo, Benedict thanked the tens of thousands of people gathered there on Thursday for "surrounding him with warmth".
"I am simply a pilgrim who is ending his path on this earth," he said. "Let's go forward in prayer with Christ. "Thank you and good night."
And in a final message from his own Twitter account, Benedict said: "Thank you for your love and support. May you always experience the joy that comes from putting Christ at the centre of your lives."
Benedict, who was elected as pope on April 19, 2005, earlier met cardinals from around the world in his final hours as leader of 1.1 billion Catholics, and promised "unconditional reverence and obedience'' to his successor.
He urged his cardinals to work in unity so that the College of Cardinals is "like an orchestra'' where "agreement and harmony'' can be reached - a clear message to the conclave that will pick the next pope.
He said he would pray for the cardinals in coming days and weeks as they choose his successor.
Between Benedict's resignation and the election of the next pope, the cardinal, referred to as the "Chamberlain", Italy's Tarcisio Bertone, will run the day-to-day affairs of the church.
On Monday the Cardinals will meet and determine the date of the conclave that would choose the 266th pope.
An estimated 100 cardinals were present at the private meeting, Al Jazeera's Paul Brennan reported from Rome.
The 85-year-old German-born pope is the first pontiff to resign since the Middle Ages.
Benedict stunned the world when he announced his momentous decision in a surprise speech in Latin on February 11, saying he no longer had the "strength of mind and body" to carry on in a fast-changing modern world.
"I took this step in full awareness of its gravity and novelty but with profound serenity of spirit," the pope told a cheering crowd of 150,000 pilgrims in St Peter's Square in his final public farewell on Wednesday.
The theologian pope - a shy academic whose papacy has been overshadowed by infighting within the Roman Catholic Church and a sex-abuse scandal - said his eight-year pontificate had seen "sunny days" and "stormy waters" but added: "I never felt alone".
The Vatican has said that the moment the pope's powers officially expire at 19:00 GMT, or at 8pm, the ex-pontiff will officially be known by the new title of Roman Pontiff Emeritus although he will still be addressed as Your Holiness.
He will also keep his papal name of "Benedict XVI" and will not be referred to his original name Cardinal Joseph Ratzinger.
Vatican analysts have suggested Benedict's sudden exit could set a precedent for ageing popes in the future, and many ordinary Catholics say a more youthful, pastoral figure could breathe new life into a Church struggling on many levels.
From Catholic reformers calling for women clergy and for an end to priestly celibacy, to growing secularism in the West and ongoing scandals over sexual abuses by paedophile priests going back decades, the next pope will have a tough agenda.