Tens of thousands of Muslims, mostly men and children, poured into open prayer grounds and mosques to offer morning prayers to mark the end of the month-long Ramzan fasting.
Merriment followed the end of prayers. People hugged one another in keeping with tradition. In many areas, Muslims and non-Muslims greeted one another to mark Eid.
People then feasted on tantalising varieties of 'sevaiyan' (vermicelli pudding), 'firni' (rice pudding), meat and biryani, prepared specially for the day.
In Delhi, tens of thousands thronged the three biggest mosques - the 17th century Jama Masjid and Fatehpuri Masjid in Old Delhi and the Idgah mosque in central Delhi.
"The prayers began at 9 and got over in 15-20 minutes," Moulvi Mohammed Mouazzam Ahmed, the Naib Imam of Fatehpuri mosque, told IANS.
"The mosque was overflowing with worshippers and so were the streets all around it, almost up to Town Hall. I believe there were one lakh people in all... There was joy everywhere."
Many foreigners, diplomats as well as refugees, also joined the prayers and festivities. Special prayers were offered in numerous embassies in the capital.
Similar scenes were reported from all over the country, particularly in states with large Muslim populations like Jammu and Kashmir, Bihar, Assam, Uttar Pradesh, Kerala, West Bengal and Andhra Pradesh.
In the Kashmir Valley, thousands gathered at grounds and mosques to pray for peace. Large gatherings packed the Hazratbal shrine, Eidgah grounds as well as Polo grounds.
Many wore new clothes, and shopped after the prayers.
Both Jammu and Kashmir Chief Minister Omar Abdullah and separatist leader Mirwaiz Umer Farooq offered prayers in Srinagar.
Street protests erupted in parts of Srinagar after Eid prayers.
In Uttar Pradesh, the country's most populous state, the festival was celebrated with traditional enthusiasm.
Aishbagh Eidgah - the biggest prayer ground in the Lucknow city - as well as mosques in the city overflowed with the devout.
"We prayed for the country's prosperity and communal harmony," Maulana Khalid Rasheed Firangi Mahli, a prominent Sunni cleric who heads Lucknow's oldest Islamic seminary, said.
Eid was also celebrated in Allahabad, Varanasi, Bareilly, Varanasi and Agra. The Taj Mahal, which houses a mosque, was opened for free for three hours Wednesday morning.
Muslims gathered at the historic Jama Masjid in south Mumbai. Prayers were held all over the city.
Qari Waqar Ahmed, who led the Eid prayers at Chhota Masjid in Mumbai, appealed to Muslims to have faith in communal harmony and not be misled by calls for jehad.
In some places, more than one round of prayers were held to accommodate the huge rush. Eid was celebrated in Bhiwandi, Malegaon, Nashik, Aurangabad, Raigad and Ratnagiri.
Eid was similarly celebrated in southern India, Assam, Orissa, West Bengal, Jharkhand, Chhattisgarh, Madhya Pradesh, Gujarat, Punjab, Haryana, Himachal Pradesh and Rajasthan.
Thousands clad in new attire and wearing skull caps offered Namaz-e-Eid Hyderabad, Warangal, Karimnagar, Nizamabad, Adilabad, Kadapa, Kurnool and other parts of Andhra Pradesh.
Malayalam superstar Mammootty joined the prayers in Kochi in Kerala, a quarter of whose population is Muslim. Eid celebrations were reported from all over Tamil Nadu.
In Assam, non-Muslims greeted Muslims in the state capital Guwahati. Reports of celebrations came from all districts of Bihar. Thousands joined prayer meetings in Gujarat and Rajasthan.