"I can say today that not one horse in NSW is now known to have equine influenza," said state Primary Industries Minister Ian Macdonald.
The minister called it a major milestone in the campaign to eradicate the disease.
The announcement comes less than six months after the first horse was infected.
"The fact that not one property has tested positive to EI since December 21 shows the success of the government's containment and vaccination strategy and the massive effort of the NSW Department of Primary Industries," he said.
"In November, at the height of EI, more than 41,000 horses were infected on more than 5800 properties.
The government, he said, had spent more than $A46 million on containment efforts and more than 100,000 horses had been vaccinated.
"EI caused great hardship to our thoroughbred and equestrian riding sectors and their associated industries.
"Today is a tribute both to the people who have been directly engaged in the battle against EI and the horse industries and the thousands of horse owners across the state whose vigilance, discipline and co-operation have been critical to stopping the spread of the virus.
"It also demonstrates that NSW has the skills and capacity to deal with a major exotic animal disease."
The minister said the government was on track to achieve its ultimate goal of totally eradicating EI from NSW by mid-March.
"We have come a very long way in the battle against this disease since the outbreak was first confirmed in August last year.
"Today's announcement is a fantastic result - there's no doubt about that.
"There are just a few more weeks for horse owners to be vigilant - we still have some way to go before we can declare NSW officially free of the EI virus and achieve 'proof of freedom' status, but the finish line is now clearly in sight.
"Extensive testing is ongoing to ensure we have not missed any isolated pockets of disease and it is vital that horse owners remain vigilant, report any sick horses and observe movement restrictions.
"This is particularly important in the purple zone where proof of freedom testing and vaccination of uninfected horses are continuing on track towards allowing us to progress the State to infection free status by mid-March."
As part of the EI campaign the state government has:
"This is another major milestone in our on-going programme to control and eradicate the disease," said state Premier Anna Bligh.
At the height of the virus outbreak, there were around 2200 infected properties.
Ms Bligh said that during the next six weeks the Department of Primary Industries and Fisheries would be conducting an intensive surveillance operation in a move aimed at accelerating Queensland towards being declared Equine Influenza free.
"A total of 1080 properties will be sampled throughout the amber and red zones.
Queensland's chief veterinary officer Dr Ron Glanville said more than 500 properties have already been contacted since Sunday.
"The surveillance team has a huge job to do over the coming weeks and we cannot do this alone.
"We ask that people be patient and cooperate with the [department] if they receive a phone call, and work in with the government appointed veterinarians who visit their property to conduct the surveillance testing."
Dr Glanville said there have been no new cases of infection confirmed since Christmas Day.
"There are still some suspect status properties where horses may have previously shown flu-like symptoms but initial tests were negative. Final results test results on those properties must be received before absolute clearance."