EU and Ukrainian officials signed the agreement today at a summit of leaders of EU nations and six post-Soviet countries.
The deal requires Ukraine to adopt a series of reforms including anti-corruption measures to remedy structural problems in its economy.
Ukraine's economy contracted by nearly 18 percent in the first quarter of 2015 from a year earlier as the country struggled with the impact of unrest in the industrial heartland of the east.
At the Riga summit, the EU also promised grants of 200 million euros (USD 223 million) to support small and medium-sized businesses in Ukraine, Georgia and Moldova.