A Harley-Davidson rider from Germany holds a souvenir depicting Pope Francis before a mass led by the Pope at Saint Peter's Square in Rome. REUTERS/Max Rossi
Bikers sat alongside nuns and other members of the large congregation, turning the famous square into a giant and noisy parking lot, BBC reports.
The Pope blessed the motorcyclists without referring to them directly.
Thousands of Harley riders are in the Italian capital for the anniversary, attending concerts and taking part in a parade.
Last week Harley-Davidson gave the pontiff two white classic ''Hogs'' for the Vatican police force to use.
The Pope delivered a pro-life sermon, offering prayers "for every human life, especially the most fragile, defenceless and threatened', without speaking directly about abortion or contraception.
