Which Philistine king did Isaac go to at Gerar during a famine?

Answer: Abimelech

Isaac went to Abimelech king of the Philistines in Gerar.

“Now there was another famine in the land, subsequent to the one that had occurred in Abraham’s time. And Isaac went to Abimelech king of the Philistines at Gerar.”— Genesis 26:1 (BSB)