Chief Minister Manohar Parrikar made the announcement today.
The referendum on whether to merge with neighbouring Maharashtra was held on January 16, 1967.
"The government has decided to celebrate the opinion poll day as Asmitai Dis. This was the only referendum held in Independent India," Parrikar told reporters, adding that due to its outcome, Goa kept its separate identity.
"Therefore the day has to be recognised and also the people who were involved with it," he said.
When the referendum was held, the then ruling party, Maharashtrawadi Gomantak Party (MGP), was in favour of becoming a part of Maharashtra. But several leaders, led by Jack Sequeira of United Goans party, were opposed to it.