The Baltic city of just over 710,000 will share the 2014 title with Swedish city Umeå, which was nominated last week (EurActiv 11/09/09).
Latvia's capital has long been a key centre for trade, finance and culture thanks to its location on the Baltic Sea as a gateway between East and West, and its historic centre has been designated a UNESCO World Heritage Site.
The city beat rivals Cesis and Liepaja to win the nomination.
Hailing the result, Mayor of Riga Nils Usakovs was quoted by DPA as saying "the fact that we have this opportunity is important not only culturally but also economically".
"We will start work tomorrow, and with this status Riga will gain five years to advertise [itself] in the East and in the West," Usakovs said, adding that he was talking to private companies about working together with the authorities to promote the year.
EU Culture Commissioner Ján Figel', meanwhile, expressed his "delight" over Riga's selection and hailed "the beginning of a great adventure," pointing to the city's "great potential" as a European cultural capital.
"Bearing this title for one year will certainly place the city in the spotlight and create enormous potential for it to develop locally and raise its profile across Europe," Figel' said.
The commissioner warned, however, that success would not be automatic. "To benefit fully, Riga will have to develop its programme for 2014 and be given all the political and economic support needed," he said.
Indeed, few details about Riga's bid were available at the time of publication, as unlike its Swedish counterpart, the city does not yet appear to have a website dedicated to its candidacy.
Umeå and Riga must still be formally designated as Europe's 2014 cultural capitals by the EU's Council of Ministers. But the Council's endorsement, expected in May 2010, is considered a procedural formality.
Last May, EU culture ministers confirmed Košice (Slovakia) and Marseille (France) as European culture capitals for 2013 (EurActiv 13/05/09).