A special committee led by the army's chief rabbi said Goldin, who held the rank of lieutenant, had been "killed in battle in the Gaza Strip on Friday", according to a statement.
An army spokesman refused to say whether the soldier's remains had been found.
The Israeli side had previously suggested that 23-year-old Goldin had been captured by Hamas fighters in Gaza, sending chances of a more permanent ceasefire nose diving. Such captures are considered by Israel to be casus belli.
Hamas's armed wing, the Ezzedine al-Qassam Brigades, had acknowledged its militants staged an ambush early Friday in which two other Israeli soldiers were killed, but denied holding Goldin.
"We have lost contact with the mujahedeen unit that was in that ambush, and we think that all the fighters in this unit were killed by Zionist shelling along with the soldier, who the enemy says is missing," it said on Saturday.
Both Israel and Hamas vowed Saturday to continue their bloody 26-day confrontation in Gaza, shunning efforts to broker an end to the bloodshed which has claimed more than 1,700 lives.