The billionaire Lee was found guilty of bribery, embezzlement, hiding assets overseas, concealing profit from criminal acts and perjury by a court in Seoul, South Korea.
Revelations of Lee's attempt to bribe South Korea's president to further his business ambitions fed public anger that led to the ouster of Park Geun-hye as South Korea's leader.
The court said Lee, 49, hoped bribes for Park and her close friend Choi Soon-sil would secure government support for a merger of two Samsung units that strengthened Lee's control over the conglomerate.
Samsung, South Korea's largest business group, has acknowledged making contributions to two foundations as well as a consulting firm linked to Choi Soon-sil, a close confidante of the embattled South Korean leader who is also facing corruption charges.
At a December parliament hearing, Lee denied that the company paid bribes to pave the way for a merger in 2015.
Samsung made the biggest contributions of $16.8m to Choi's foundations.
Samsung is separately accused of funnelling millions of dollars to Choi to bankroll her daughter's equestrian training in Germany.
Prosecutors said the donations were made in exchange for government favours, allegations that Lee and Choi had denied.
Other former Samsung executives charged with Lee were also found guilty.
Choi Gee-sung, Lee's mentor, and Chang Choong-ki were sentenced to four years in prison. Two other former executives received suspended jail terms.