Orbiters 13 and 14 blasted off on a Russian Soyuz rocket from Europe's spaceport in Kourou, French Guiana, at 0848 GMT as planned, according to space agencies.
After a journey of nearly four hours, the 700-kilogramme (1,540-pound) satellites entered Earth orbit at an altitude of 23,522 kilometres (14,615 miles).
"Named for the astronomer who pinpointed the Earth's true position in the Solar System, the Galileo satellite navigation system that will help Europe find its way in the 21st century now has 14 satellites in orbit," the European Space Agency (ESA) said.
Ultimately, the multi-billion-euro constellation named after the "father of modern science" is meant to comprise 30-odd satellites -- the final number is yet to be determined -- providing navigation and search-and-rescue services.
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"This morning's launch... Marks a further step towards European independence in satellite navigation," said Stephane Israel, chairman of launch firm Arianespace.
Another launch, this time of four orbiters on a single rocket, is expected to boost the constellation to 18 by year-end, allowing for Galileo to start providing usable signals.
More modern than the US Global Positioning System (GPS), Galileo's high-tech instruments should allow it to provide a more precise signal, its developers say.
But the project has been plagued by delays, technical glitches and budgetary difficulties.
The launch of the seventh and eighth orbiters in March last year was about three months late to allow engineers time to probe an August 2014 mishap which sent satellites five and six into a lopsided orbit.
That incident was blamed on frozen fuel pipes on the Soyuz rocket's fourth stage, called Fregat -- a problem the ESA says has since been fixed.
In March 2013, the quartet managed to pinpoint their first-ever ground location with an accuracy of between 10-15 metres (32 to 49 feet).