Eli's worthless son whose disrespect of the sacrifice brought a curse onto Eli's house. He was killed with his brother.
He did not know the LORD and despised the sacrifices and lay with the tent of meeting's maidservants. Ultimately, a man of God told Eli he would be withdrawing his selection of his house as a priesthood and raise a new, faithful priest. There would be no old man in his house, his descendants would die by the sword, they will be envious of the prosperity of Israel, and only one will remain to weep. Hophni and Phinehas shall die on the same day as a sign. (1 Samuel 2)
He went with his brother and the ark of the covenant to reenter battle with the Philistines after a substantial loss near Ebenezer and Aphek, killing 4000 Israelites. The Philistines won again anyway, capturing the ark of the covenant and killing both Hophni and Phinehas. (1 Samuel 4)