The hard-fought agreement cleared the way for at least a decade of negotiations aimed at bringing into the EU a mainly Muslim country with a population of 70 million and a land border with Iraq.
Turkey first knocked on Europe's door in 1963 when it signed an association agreement with European Economic Community and Ankara's long journey is far from over. Both France and Austria intend to hold referendums before any decision to give final approval to Turkish entry.
But yesterday's decision could be one of the most far-reaching taken since France, Germany, Italy, the Netherlands, Belgium and Luxembourg, first embarked on their experiment in European integration half a century ago. A project originally designed to heal the divisions in Europe is now in the vanguard of efforts to build bridges between the West and the Islamic world.
Britain, which holds the EU presidency, battled for hours to overcome an internal rift which took Europe to the brink of a deep crisis. Austria, the leading sceptic on Turkish accession, had demanded a series of changes to the negotiating mandate for talks. Though it won only one relatively minor change, its ally, Croatia, was given the green light for EU membership talks.
That paved the way for the breakthrough on Turkey. In the wake of the terrorist attacks in the US in 2001, in Madrid in 2004, in London in July this year and on Saturday in Bali, embracing a modernising, secular state with a mainly Muslim population is seen as a key signal of reconciliation.
The Foreign Secretary, Jack Straw, said: "It is truly an historic day for Europe and the whole of the international community. Every enlargement that has taken place within the EU made both the existing members and the new member states both stronger and more prosperous. I have no doubt that these benefits will flow from this enlargement. It will bring a strong, secular state which happened to have a Muslim majority into the EU. This is proof that we can live and prosper together."
The sight of the EU almost tearing itself apart over Turkey's European ambitions took some gloss off the decision.
But last night Turkey's government accepted the terms on which the negotiations will take place, after raising last-minute objections to the changes to the text on the table.
Vienna failed in its bid to keep open the possibility of a second-class status for Turkey. Behind the scenes Austria faced massive pressure, including private threats from the United States a strong backer of Turkey.
The EU also gave the go-ahead to the launch of membership negotiations by Croatia an ally of Austria. The prospect of membership talks for Zagreb smoothed the way for Austria to back down over Turkey.
Late in the day Ankara protested about a passage in the text which, it believed, might imply its agreement to future applications by Cyprus to international bodies such as Nato. That provoked frantic telephone diplomacy as Ankara indulged in a show of 11th-hour brinkmanship and the EU put out a statement to clarify the issue.
Last night's deal marks only the beginning of a lengthy and difficult path for the Turks towards EU membership.
Formal negotiations will stretch out over more than a decade, and Turkey will have to meet rigorous standards laid down in more than 80,000 pages of text. To qualify for membership Ankara will have to close agreements with the EU over 35 different areas of policy.
To do that, it will have to convince both the European Commission and a committee of representatives from each of the member states that it has complied with EU requirements.
That may be no easy task since several member states are likely to take a tougher line with Turkey than with previous enlargements. In addition to Austria, a possible change of government in Germany is likely to lead to a harder position.
Moreover, the pledge by France and Austria to hold referendums before giving final approval for Turkey to join the EU poses another huge obstacle.
The long and winding road to unity
* 1951 France, Germany, the Benelux states and Italy sign a treaty to establish the European Coal and Steel Community (ECSC).
* 1957 Signing the Treaty of Rome the six ECSC members set up the European Economic Community (EEC), a customs union for free move- ment of capital and labour.
* 1973 Britain, Denmark and Ireland join the EEC.
* 1981 Greece joins the EEC.
* 1986 Portugal and Spain join and the European flag is unveiled.
* 1991 The European Union emerges from the Maastricht treaty, which paves the way for a monetary union. The treaty comes into effect two years later.
* 1995 The Schengen pact relaxes border controls as Austria, Finland and Sweden join the EU.
* 2002 The euro, the single currency, is launched in 12 participating states. The UK, Sweden and Denmark stay out.
* 2004 Latvia, Hungary, Lithuania and seven more countries join the EU, which has now 25 member states.
* 2005 France and the Netherlands vote against the new EU constitution.Reuse content