On July 11th, 2015, Satoru Iwata, Nintendo's fourth president and Chief Executive Officer (CEO) passed away after complications following surgery. Iwata was the face of Nintendo, highly respected by the community and widely regarded as a major contributor in what brought Nintendo games to new audiences.
The man that will be attempting to fill Iwata's shoes is Tatsumi Kimishima, an executive that has been a part of Nintendo since 2000. His name might not be recognizable off-hand, but Kimishima has held a number of roles and responsibilities at the company and the video game world.
In 2000 Nintendo appointed Kimishima as The Pokemon Company's Chief Financial Officer, in 2001 he became the president of Pokemon USA – during his time Pokemon Gold and Silver and Pokemon Crystal made their release.
In 2002 Kimishima became the President of Nintendo of America, where he was promoted to CEO and Chairman of the Board. Until the announcement of succeeding Iwata, Kimishima held these positions, as well as being the Managing Director of Nintendo.
TL;DR: Tatsumi Kimishima has been named the President of Nintendo.