Men, women and children crowded Shiva shrines in towns, cities as well as rural areas. The bigger and more popular Shiva temples saw serpentine queues of devotees, each carrying offerings for the Lord.
The solemn celebrations will conclude early on Saturday.
On this day, devotees offer oblations of water, milk, honey, curd and sandal paste on the Shivling and flowers and fruit, especially the Bel fruit.
Across the country, innumerable Hindus fasted on Friday. Some avoided their normal food and consumed only fruits while others did not even sip water.
Hindu temples across the country were decorated with bright lights and colourful decorations.
Reports of Maha Shivratri celebrations came from all over the country, ranging from Hindu pockets in the Kashmir Valley to the southern states and from Gujarat to Assam.
There were huge crowds at the Jyotrilings including at Somnath (Gujarat), Ujjain (Madhya Pradesh), Deogarh (Jharkhand), Rameshwaram (Tamil Nadu), Kedarnath (Uttarakhand), Varanasi (Uttar Pradesh), Srisailam (Andhra Pradesh) and Trimbakeshwar (Maharashtra).
Devotees also thronged pilgrimage centres including Haridwar, Rishikesh and Varanasi. In Nepal too, devotees thronged temples.
The prayers and offerings at major Shiva temples are to continue through the day. The more ardent devotees would keep awake praying the whole night.
The Maha Shivratri prayers will formally end around dawn on Saturday.