.jpg)
Masses were celebrated hourly in a small church on the summit of Croagh Patrick from 8am until 2pm and confessions also took place on the summit.
Pilgrims have been climbing the 765-metre-high mountain for more than 1,500 years.
St Patrick is said to have spent 40 days and nights fasting on its summit in 441.
Stewards, mountain rescue teams, the Order of Malta, and gardaí, are on standby during the physically demanding pilgrimage.
While it is a custom for some to scale the iconic mountain in their bare feet, pilgrims have been advised to come prepared for changeable weather conditions.
Many football fans scaled the reek early ahead of this afternoon's All-Ireland Final between Mayo and Kerry.
In a homily in Saint Mary's Church, Westport last night, Archbishop of Tuam and Bishop of Killala Francis Duffy said road safety was the theme chosen for this Reek Sunday.
Archbishop Duffy said behind every statistic lies "trauma, heartache and sadness", adding lives and families can be changed in a single moment.
"Taking care on the road is an essential part of respect - respect for ourselves and for others: our passengers, and every driver, cyclist and pedestrian who shares the road with us," he said.
He said while there are many careful and responsible drivers, a vehicle of any kind is also dangerous, and it demands responsible handling.
"Slowing down, leaving in good time, resting when needed, staying sober and staying focused, obeying the rules of the road - these are not accidentals either.
"They are the essentials. They are the fruit of a deliberate decision to be more careful and to respect others," he said.