Lee, 54, has been vice chairman of Samsung Electronics, the crown jewel of South Korea's biggest business conglomerate, since 2012.
That is a major business risk for Samsung, which counts both China and the United States as major markets.
But Samsung insiders say his quiet, urbane manner disguises a steely determination Lee will need if he is to grow Samsung.
As an only son, Lee was groomed by his father to take over the core business of Samsung Group, which his grandfather founded in 1938.
Shares in construction affiliate Samsung C&T (028260.KS), in which Lee owns a 18% stake, rose as much as 7.1%.