King of Jacob is an alternative title to king of Israel. God changed Jacob’s name to Israel and that became the name of the twelve-tribe nation. God was Jacob’s king but He was also king of the entire nation and the world.
King of Jacob in Hebrew:
Strong’s Concordance numbers: 4428, 3290
Bible reference: Isa. 41: 21
Produce your cause, saith the Lord; bring forth your strong reasons, saith the King of Jacob. (Isaiah 41: 21 KJV)
Similar royal names for God are King of kings, King of heaven, King of the nations, King of glory. Jesus (Yeshua‘) was also called King of the Jews.