Israel defends blocking fuel deliveries, as the UN warns this could lead to a breakdown of civil order.
Telecom firms Paltel and Jawwal said all energy sources sustaining their networks were depleted, and an internet monitor confirmed a major outage.
Israel has blocked all but one delivery of fuel to Gaza since the start of its war with Hamas five weeks ago.
The UN said a blackout could jeopardise civil order and undermine aid efforts.
"We regret to announce that all telecom services in Gaza Strip have gone out of service as all energy sources sustaining the network have been depleted, and fuel was not allowed
Since Israel started its counterattack, Gaza's Hamas-run health ministry has said 11,400 people have been killed in the territory and the United Nations has warned of a "humanitarian disaster".
The Israeli government has defended blocking fuel deliveries during its campaign, saying it is concerned that Hamas could steal fuel and use it for military purposes.
One tanker carrying 23,000 litres of diesel crossed from Egypt on Wednesday, but Israel restricted its use only for the refuelling of UN aid lorries.
Other key services have already had to shut down because of similar issues. This includes hospitals, water pumps, desalination plants, sewage treatment facilities and bakeries
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