He was found guilty of bribery, embezzlement, hiding assets overseas, concealing profit from criminal acts and perjury, Al Jazeera reported.
Lee, the acting chairman of Samsung, had been accused of paying 41 billion won (US$38 million) in bribes - hidden as donations – to non-profit foundations controlled by a close friend of South Korea’s ex-president Park Geun-hye, the Guardian reported.
Prosecutors believe the donations were made to win government blessing for a 2015 Samsung merger that would strengthen Lee’s control over the conglomerate, which he had been running since his father suffered a heart attack the year before.
Many of Samsung’s shareholders opposed the US$ 8 billion merger, but it went ahead after the national pension fund – a major Samsung shareholder – approved it.
Although his five-year sentence is less than the 12 years that prosecutors had asked for, judges reportedly believe the total amount of bribes was less than US$ 38 million, according to Al Jazeera.
Nevertheless, it is still the longest prison sentence given to any South Korean business leader, who have historically received light sentences for corruption.
Lee’s father, Lee Kun-hee, was convicted of tax evasion in 2009 but was pardoned just four months later. Judges praised his contribution to South Korea’s economic success and his "patriotism through business enterprise from job creation," according to the Guardian.
The scandal has led to huge public protests and growing anger against many of South Korea’s largest companies, the BBC reported.
It has been described as the "trial of the century" by local media, and more than 450 people applied for the 30 seats in the public gallery for Friday’s ruling, according to the Guardian.
Lee has repeatedly denied the charges since his arrest in February, claiming he had little involvement in the day-to-day running of Samsung.
However, Friday’s court ruled that he had approved donations to the foundations belonging to the president’s confidante, Choi Soon-sil, which were allegedly set up to support Park’s policy initiatives.
The company itself has not denied the donations, but claimed it had been forced to do so by the former president.
The ruling leaves a leadership void at Samsung, whose shares fell by 1 percent within hours of the verdict, the BBC reported.
Choi has already been jailed for three years for corruption.
Park, who indicted last year, faces a possible life sentence.
Four other former Samsung executives have also been found guilty, including Lee’s mentor, Choi Gee-sung, who received four years in prison for corruption, according to Al Jazeera.
