A special committee led by the army's chief rabbi said Lieutenant Goldin had been "killed in battle in the Gaza Strip on Friday", the Israeli armed forces said in a statement.
Military radio said that no body had been recovered, adding that this made the decision to announce Goldin's death a "very delicate" one.
There was no government word on the whereabouts of the soldier's remains.
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 in the bloody offensive nosediving. 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.
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.
With no resolution in sight, a senior Palestinian delegation landed in Cairo for talks Sunday on an Egyptian ceasefire initiative, but Israel said it was not sending a negotiating team.
"Hamas has proven that it breaches any agreement reached right away, as happened five times in previous truces," deputy foreign minister Tzahi HaNegbi told AFP.
"It is therefore unclear at this stage what benefit Israel might see for participating in an attempt to reach agreements, based on the Egyptian initiative," he added.
US Middle East envoy Frank Lowenstein is expected to arrive for talks, along with representatives of both Hamas and Islamic Jihad.
The Gaza violence has claimed 1,720 Palestinian lives and displaced up to a quarter of the territory's population.
Goldin's death brings Israeli army deaths to 64 since the start of hostilities on July 8, its heaviest toll since the 2006 war against the Lebanese Hezbollah.