In a statement, Suresh Kumar, Microsoft's corporate vice-president for cloud infrastructure and operations, said the subsea cable was the most technologically advanced to cross the Atlantic Ocean.
The cable runs for more than 6600 kms and weighs about 4.65 million kgs – or about the weight of 34 blue whales.
It can transmit up to 160 terabits of data per second, making it 16 million times faster than the average US home Internet connection.
The installation of the Marea subsea cable began last year.
It was also the first to connect the US state of Virginia with Spain, with the landing being in Virginia Beach and Bilbao.
Kumar said the cable's new "open" design would allow it to evolve with technology, as the number of Internet users increased globally.
"And make no mistake, the demand is growing. Just think of the many high-bandwidth applications and content you use today such as Skype and Facebook Live, and the volume of streaming videos, movies and music consumed daily," he said.
"This ability to interoperate with many different kinds of networking equipment brings significant benefits including lower costs and easier equipment upgrades, leading to faster growth in bandwidth rates."
The Marea cable coiled onboard a ship.
The name of the cable, Marea, means "tide" in Spanish.
Microsoft's Deborah Bach said: "Situating the cable many miles south of the current connection points on both continents helps to safeguard against natural disasters or other major events disrupting connectivity across the Atlantic."
Bach said that the project required charting a course with average depths of almost 11,000 feet (3352 metres) and hazards ranging from active volcanoes and earthquake zones to coral reefs.
"The cable, which is about 1.5 times the diameter of a garden hose, contains eight pairs of fibre optic cables encircled by copper, a hard-plastic protective layer and a waterproof coating. Some portions closer to shore are buried to protect the cable from fishing and ship traffic, but for most of its route, the cable lays on the ocean floor," she added.
Graphic and photos: courtesy Microsoft