The Association Agreement is intended to tie Ukraine closer to the European Union. Political and economic ties would be strengthened and the former Soviet republic gradually integrated into the European Union market.
The agreement, which has already partially entered into force, includes a reform agenda for Ukraine, which is expected to bring its laws into line with EU norms.
The agreement also foresees reforms to strengthen democracy and the rule of law, as well as protection for human rights and measures to combat corruption.
The agreement sparked the political crisis that erupted in Ukraine in November 2013 and the subsequent tensions with former ruler Moscow.
Following pro-European demonstrations in the capital Kiev's central Maidan (Independence) Square, the pro-Russian president Viktor Yanukovych was toppled from power.
Russia vehemently protested the rapprochement between Ukraine and the EU.
The Association Agreement includes a free-trade agreement, which targets an almost 100-per-cent dismantling of trade tariffs on both sides.
Ukraine has agreed to adapt its regulations to the EU's to facilitate trade and to open up inward investment and guarantee free capital flows.
EU firms will gain easier access to a sales market of some 45 million consumers, and the end of tariffs is expected to save them hundreds of millions of euros in costs annually, according to estimates by the European Commission.
Moscow has expressed concerns that its economy will be negatively impacted by the agreement, as tax-free imports from the West could enter Russia via Ukraine.