Lee was arrested earlier this year after Samsung's involvement in President Park Geun-hye's scandals came to light. Two other Samsung executives were also convicted in the same trial and will serve four year sentences.
Lee is accused of giving W43.3 billion in bribes to ex-President Park Geun-hye and her confidante Choi Soon-sil (US$1=W1,129).
In his defence, Lee's lawyers said Samsung was compelled by Park to support the national equestrian team, which happened to include Choi's daughter, and to make the donations to support the country's cultural and sports development.
The ruling on Park, South Korea's first female president, is expected in October.
Lee Jae-yong, Samsung's acting chairman, has been sentenced to five years in prison for bribery by a South Korean court.
Samsung and Lee deny the charges and claim the deals were to boost the business' competitiveness. Experts believe that Lee is not a global face of the brand, and that is why the verdict will not affect the business much.
The court sentenced Lee to five years in prison.
"Samsung Electronics represents South Korea as a global company so we are deeply anxious about the fallout from his long absence", said a Korea Employers Federation spokesman.
He stood accused of offering millions of dollars to former president Park Geun-hye, who is now undergoing her own trial, and business partner Choi Soon-sil, in exchange for favourable businesss conditions. Previously both politicians and chaebol leaders were handed with light charges in similar cases.
Samsung's offer of 1.63 billion won to a Choi-controlled children sports center was regarded by the court as bribery. Park was impeached in March and is herself separately on trial. The vice-chairman of Samsung Electronics, 49, arrived at Seoul Central District Court on a justice ministry bus handcuffed, bound with white rope around his dark jacket, and carrying an envelope of documents. In total, Samsung paid £6.1 million to the German company, the judges said.
Via her friendship with Park, Choi was found guilty of meddling in state affairs, as well as wielding influence over large conglomerates in the country. Two other former executives received suspended jail terms.