Who said he would exalt his throne above God's throne?

Satan, also known as Lucifer:

Isaiah 14:12-1512How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!

13For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north:

14I will ascend above the heights of the clouds; I will be like the most High.

15Yet thou shalt be brought down to hell, to the sides of the pit.