The song, originally recorded in 1964, was written in the 1840s by Thomas Osbourne Davis to support the fight for an end to British rule.
The winning song was recorded by The Wolfe Tones and includes the refrain: "And Ireland, long a province, be a nation once again".
Following a late surge in votes, the Irish sing along crossed the finishing line ahead of a patriotic Hindi song, Vande Mataram.
1. A Nation Once Again, The Wolfe Tones
2. Vande Mataram, Various artists
3. Dil Dil Pakistan, Vital Signs
4. Rakkamma Kaiya Thattu, llayaraaja
5. Poovum Nadakkuthu Pinchum Nadakkuthu, Thirumalai Chandran
6. Ana wa Laila, Kazem El Saher
7. Reetu haruma timi hariyali basant hau nadihruma timi pabitra ganga hau, Arun Thapa
8. Believe, Cher
9. Chaiyya chaiyya, A R Rahman
10. Bohemian Rhapsody, Queen
The Wolfe Tones were said to be "thrilled" by the announcement.
They said they were "proud" to have been ranked above bands such as The Beatles, who failed to make the top 10 despite 55 different song nominations.
With the lyrics taken from a poem written by Bankim Chandra Chatterjee, Vande Mataram is regarded by many as India's national song.
In third place an Asian track, popular in the 1980s, entitled Dil Dil Pakistan by Vital Signs, finished ahead of pop poll classics including Cher's Believe at number eight and Queen's Bohemian Rhapsody at number ten.
A few artists had many songs nominated and split their vote.
Forty songs by Iranian artist Googoosh were chosen while Bob Marley had 29 songs nominated, with No Woman No Cry topping the list.
Cher's Believe came in at number eight
Europe's top tune was Wind of Change by the Scorpions, a song many associate with the fall of the Berlin Wall.
Also popular was this year's summer holiday hit The Ketchup Song by Spanish sisters Las Ketchup. Abba and fellow Scandinavians Ace of Base had songs nominated too.
Since its launch in November the poll, which was part of BBC World Service's 70th anniversary celebrations, attracted the attention of listeners from all around the world.
From Botswana and Antarctica to the Caicos Islands, nearly 150, 000 votes were received from 153 countries, nominating over 6, 500 songs.
By inviting its 150 million listeners to vote either by post or online, organisers were surprised by the scale of the voting.
BBC World Service 70th anniversary project editor David Stead, said: "It's been a massive logistical challenge."
The poll had to deal with people trying to influence the vote through fan sites and spamming.
"Our New Media teams have been stretched to the limit and it has been extraordinary watching the votes drop in second by second into our mailbox."