The vast crowd of pilgrims packed St Peter's Square and spilled onto the surrounding streets.
Millions of others watched the Mass on television, many gathering around giant screens in cities around the world.
After the requiem, the coffin was taken back into the basilica and placed in its final resting place in the crypt.
Only senior clerics and close friends of the Pope accompanied to coffin to the 16th Century crypt for the private interment.
The three-hour funeral service was conducted by Cardinal Joseph Ratzinger, dean of the Sacred College of Cardinals, which will begin electing the Pope's successor on 18 April.