Gennady Sipachyov, a Russian citizen whose age and profession have been kept secret, was found guilty of "state treason in the form of espionage" and sentenced to four years in a maximum-security prison camp.
His crime, which Russia's FSB security service said he had confessed to, was to email secret military maps identifying classified Russian military infrastructure to the Pentagon in 2008.
The case is embarrassing for both the Kremlin and for Washington as it comes at a time when both are trying to improve their historically-troubled relationship and not long after the two countries signed a landmark treaty cutting their respective nuclear arsenals.
Court documents released on Thursday claimed that the Pentagon's in-house intelligence service had acted under the cover of a bogus organisation called "East View Cartography" to solicit the secret maps from Mr Sipachyov in order to fine tune its targeting of strategic Russian military objects.
"The Pentagon required the maps in order to correct its guidance system for cruise missiles to increase the accuracy of targeting," the court said.
Much of the trial was held behind closed doors and Mr Sipachyov's motive for committing the crime was not cited though is thought to have been financial.
Pictures of Mr Sipachyov showed an unassuming bespectacled man wearing a worn denim shirt who looked like he would be more at home in a library rather than committing state treason. Some reports suggested he had worked at a closed academic institution.
The FSB security service said Mr Sipachyov had generously co-operated with the investigation and had therefore had his sentence sharply reduced from a possible maximum of twenty years to just four.
"Sipachyov co-operated actively in the detection and investigation and also pointed to criminal activity by other individuals which helped prevent further damage to the security of Russia," the verdict read.
Court officials said it was the first time in the history of Russian espionage that a suspect accused of state treason had struck a deal with prosecutors in exchange for a lighter sentence.
A Russian citizen identified as Gennady Sipachyov has been convicted of "state treason in the form of espionage" and was sentenced to four years in a Russian maximum-security prison.

According to the Russian intelligence agency Federal Security Service (FSB), Sipachyov was found guilty of giving the American government classified military maps, which can be used to target American missiles against targets in Russia more accurately.  According to the FSB, the exchange of of information occurred in 2008, when Sipachyov emailed the documents to an organization called "East View Cartography," which was a cover for the intelligence service of the US military.

In its verdict, the court said that "The Pentagon required the maps in order to correct its guidance system for cruise missiles to increase the accuracy of targeting."  While no motive was identified, and the trial was barred to the media, speculation has been that any motive involved was financial in nature.

Sipachyov, whose age and profession were not released, was convicted under Article 275 of Russia's criminal code, pertaining to "state treason in the form of espionage."  Such a conviction ordinarily carries a sentence of 20 years, but according to the FSB, Sipachyov had "co-operated actively in the detection and investigation and also pointed to criminal activity by other individuals which helped prevent further damage to the security of Russia," leading to his sentence being reduced.

The incident has been seen as embarrassing for both the Russian and American governments, as the two countries are currently trying to repair their previously rocky relationship.  Earlier this year, a treaty reducing the number of nuclear weapons each country held was signed.  The US government has not commented on the ruling.