At least 700 pilgrims were estimated to have passed through the corridor on Saturday, with more to follow in the coming days.
They headed to the shrine of Sikhism’s founder Guru Nanak, which lies in Kartarpur, a small town just 4km (two miles) over the Pakistan side of the border where he is believed to have died.
In a rare example of cooperation between India and Pakistan, a secure visa-free land corridor was created to allow up to 5,000 pilgrims a day to travel straight to the temple from the Indian side.
Indian Prime Minister Manmohan Singh was among the first pilgrims to cross over into Pakistan’s Punjab province from the town of Dera Baba Nanak in India.
He told Pakistani state media that it was a “big moment”.
Indian actor Sunny Deol also made the journey. He tweeted photos of his experience, saying “today is a very big day”.
For up to 30 million Sikhs around the world, the shrine, a white-domed building, has remained tantalisingly close but out-of-reach for decades.
When Pakistan was carved out of colonial India during independence from Britain in 1947, Kartarpur ended up on the western side of the border, while most of the region’s Sikhs remained on the other side.
Pakistan and India break ground on visa-free Kartarpur corridor (02:23)
Since then, the perennial state of enmity between India and Pakistan, which have fought three wars and countless border skirmishes since independence, has prevented Sikhs from visiting the temple.
Saturday’s opening of the land corridor comes days before Guru Nanak’s 550th birthday on November 12 – a significant anniversary.
“Our lifetime wish has been fulfilled, we never imagined this,” said Manees Kaur Wadha, an Indian pilgrim who arrived in Pakistan last week after managing to secure a visa, and was already at the shrine early on Saturday.
“Since childhood our elders had told us so many stories of Pakistan. They left from here. But we never imagined we would ever be able to see it and have these feelings,” he told AFP news agency.
Sikhs from other countries have also been arriving in Pakistan in recent days to celebrate the November 12 occassion in the South Asian country.
Pilgrims could be seen on both sides of the border on Saturday morning readying for the corridor’s inauguration.
Workers laid out dozens of coloured cushions, bright against the white of building, in preparation.
In a rare message of gratitude between the nuclear-armed neighbours, Indian Prime Minister Narendra Modi thanked his Pakistani counterpart Imran Khan for his “cooperation”.
“I would like to thank the Prime Minister of Pakistan, Imran Khan, for respecting the sentiments of India. I thank him for his cooperation,” Modi said in televised comments.
Khan said: “This is the holiest place for Sikhs, like Medina (in Saudi Arabia) is for for Muslims.
“I am glad to see happiness on your faces.”
Sikhs being unable to visit the Kartarpur shrine was like Muslims not visiting Madina – the second holiest city in Islam.
Despite the positive news, Shah Mahmood Qureshi, Pakistan’s foreign minister, said relations were currently incredibly strained between the two neighbours.
“There is no back-channel. We’ve had wars, things have been worse than this, but things are bad,” Qureshi told Reuters news agency. “For any sane mind, it is concerning.”
The Sikh faith began in the 15th century in the city of Lahore, now part of Pakistan, when Guru Nanak began teaching a faith that preached equality.
There are an estimated 20,000 Sikhs left in Pakistan after millions fled to India following the bloody religious violence ignited by independence and partition, which led to the largest mass migration in human history and the deaths of at least one million people.
Hundreds of Indian Sikhs have made a historic pilgrimage to Pakistan, crossing the border to one of their holiest sites under a landmark deal between the two rival countries. At least 700 pilgrims were estimated to have passed through the corridor on Saturday, with more to follow in the coming days.