The first Hokage was Hashirama Senju. The seconde Hokage was Tobirama Senju. The third Hokage(my personal fav.) was Hiruzen Sarutobi. The fourth Hokage was Minato Namikaze. The fifth Hokage is Tsunade (Senju?).
[EDIT] Danzo Shimura and Kakashi Hatake were candidates for sixth Hokage after Tsunade's assumed death after Pains invasion of Konoha.
There are 7 hokages. The 1st one is hashirama senju the seconde one is tobirama something the third is hiruzen sarutobi the 4th one is minato namakazi the 5th is tsunade senju the 6th is Kakashi hatake and the last 7th is Naruto Uzimaki
