Marcel Lazar, known online as "Guccifer", pleaded guilty in May on charges of aggravated identify theft and unauthorised access of a computer.
Lazar, who targeted former Secretary of State Colin Powell and the Bush family, was arrested on hacking charges in Romania in 2014 and given four years.
He was extradited to the US to face charges in March 2016.
The 44-year-old inadvertently uncovered Democratic presidential nominee Hillary Clinton's private email account in 2013 after hacking the account of her former political adviser, Sidney Blumenthal.
Two years later, it was revealed that Mrs Clinton exclusively used her personal account, which was connected to a private server at her New York residence, while serving as secretary of state.
Mrs Clinton's use of private email while at the State Department became the subject of an FBI investigation and has dogged her on the campaign trail.
Earlier this year Lazar claimed he had hacked into her private server, but the Clinton campaign has denied there was any such breach.
The FBI also has said there is no evidence to prove he had hacked her.
Lazar, a former taxi driver in Romania, is believed to have hacked into about 100 US email accounts between 2012 and 2014.
In June, a hacker who goes by the alias "Guccifer 2.0" claimed data breaches on the Democratic National Committee and the Democratic Congressional Campaign Committee.
US intelligence officials have said they believe Guccifer 2.0 is linked to Russian intelligence services, suggesting that the hack was state-sponsored.
There is no known connection between Lazar and Guccifer 2.0.

Sutton opened the scoring after 13 minutes when Kevin Amankwaah laid the ball back for Roarie Deacon to fire in.
Nine minutes later they were two up when Maxime Biamou headed down for Jamie Collins to volley in from 10 yards.
Biamou turned scorer 11 minutes later when he netted the third with a simple tap in after Cadogan had sent in a low cross to the far post.
North Ferriby pulled a goal back three minutes into the second half when Robbie Tinkler ran into the area, evading four defenders, before shooting into the far corner.
But any thoughts of a fightback were ended when Cadogan netted just after the hour, shooting through the goalkeeper's legs, before getting his side's fifth goal with seven minutes to go.
Match report supplied by the Press Association.
Match ends, Sutton United 5, North Ferriby United 1.
Second Half ends, Sutton United 5, North Ferriby United 1.
Goal!  Sutton United 5, North Ferriby United 1. Kieron Cadogan (Sutton United).
Substitution, Sutton United. Craig Dundas replaces Gomis.
Substitution, North Ferriby United. George Bell replaces Reece Thompson.
Reece Thompson (North Ferriby United) is shown the yellow card for a bad foul.
Substitution, North Ferriby United. Kojo Keyi replaces Mark Gray.
Substitution, Sutton United. Ben Jefford replaces Adam Coombes.
Goal!  Sutton United 4, North Ferriby United 1. Kieron Cadogan (Sutton United).
Substitution, North Ferriby United. Matthew Templeton replaces Danny Emerton.
Gomis (Sutton United) is shown the yellow card for a bad foul.
Ryan Fallowfield (North Ferriby United) is shown the yellow card for a bad foul.
Goal!  Sutton United 3, North Ferriby United 1. Robbie Tinkler (North Ferriby United).
Substitution, Sutton United. Daniel Spence replaces Kevin Amankwaah.
Second Half begins Sutton United 3, North Ferriby United 0.
First Half ends, Sutton United 3, North Ferriby United 0.
Goal!  Sutton United 3, North Ferriby United 0. Maxime Biamou (Sutton United).
Goal!  Sutton United 2, North Ferriby United 0. Jamie Collins (Sutton United).
Mark Gray (North Ferriby United) is shown the yellow card for a bad foul.
Goal!  Sutton United 1, North Ferriby United 0. Roarie Deacon (Sutton United).
First Half begins.
Lineups are announced and players are warming up.
A Romanian hacker who targeted high-profile US politicians has been sentenced to 52 months in prison.
[NEXT_CONCEPT]
Two goals from Kieron Cadogan emphasised Sutton's superiority as they thrashed struggling North Ferriby 5-1.