The British Medical Association (BMA) said 98% voted in favour of strikes, with 2% against and 11 spoilt ballot papers.
More than 37,000 doctors were balloted by the BMA, and 76% took part in the vote.
Asked if they were prepared to take part in industrial action short of a strike, 28,120 (99.4% of the vote) said yes.
Asked if they were prepared to take part in strike action, 27,741 voted yes (98% of the vote) and 564 voted no (2%).
The BMA said it was still keen to avoid strike action and had approached the Advisory, Conciliation and Arbitration Service (Acas) for talks with Health Secretary Jeremy Hunt and NHS Employers, which is running negotiations for the Government.
If a strike goes ahead, doctors will take action over three days, providing emergency care only for 24 hours from 8am on December 1, followed by full walkouts from 8am to 5pm on December 8 and 16.
There is expected to be mass disruption to the NHS, with hospitals forced to cancel outpatient clinics and non-urgent operations.
Dr Mark Porter, chair of the BMA council, said: “We regret the inevitable disruption that this will cause but it is the Government’s adamant insistence on imposing a contract that is unsafe for patients in the future, and unfair for doctors now and in the future, that has brought us to this point.
“Patients are doctors’ first priority, which is why, even with such a resounding mandate, we are keen to avert the need for industrial action, which is why we have approached Acas to offer conciliatory talks with the Health Secretary and NHS Employers to clarify the conflicting information coming from Government over the past weeks.
“The Health Secretary is right when he says this action is ‘wholly avoidable’.
“Our message to him is that junior doctors have today made their views perfectly clear but that it is still possible to get back around the negotiating table to deliver a contract that is safe for patients, contains the necessary contractual safeguards to prevent junior doctors being overworked and properly recognises evening and weekend work.”
The new contract is set to be imposed from next summer on doctors working up to consultant level.
Mr Hunt tried to avert strikes with a fresh deal, including an 11% rise in basic pay.
This is offset by plans to cut the number of hours on a weekend that junior doctors can claim extra pay for “unsocial” hours.
Currently, 7pm to 7am Monday to Friday and the whole of Saturday and Sunday attract a premium rate of pay.
Under the new plans, a higher rate would run from 10pm to 7am Monday to Friday, and from 7pm on Saturday evenings - a concession on the previous 10pm.
Other proposals are to replace the GP pay supplement - without which GPs would be paid on average around a third less than hospital trainees - and replace it with a “flexible pay premium”.
The BMA is concerned this could be removed over time and may only be offered in certain geographic areas.
Mr Hunt has said flexible pay premiums would be applied to more specialities than just general practice and A&E care, with acute medical ward staff and psychiatrists benefiting.
He argues that, under the new deal, just 1% of doctors would lose pay and those would be limited to doctors working too many hours already.
He said maximum working hours per week would fall from 91 to 72.
Dr Johann Malawana, the BMA’s junior doctor committee chairman, has said the increase in basic pay is misleading due to the changes to pay for unsocial hours. He said this devalues the vital work junior doctors do in the evenings and at weekends.
The BMA has argued the Government could avoid strikes by offering assurances and lifting the threat that the contract will be imposed.
Guaranteed pay increases linked to time in the job are being scrapped and replaced with a system linked to progression through set training stages.
The BMA argues that this affects some trainees, such as women who take time out to have a baby.
Shadow health secretary Heidi Alexander said: “Jeremy Hunt needs to take responsibility for the fact that this is the first time in 40 years that junior doctors have voted to take such significant industrial action.
“There is clearly huge anger about the way in which these negotiations have been handled by the Government.
“It is imperative that, in the next 10 days, Jeremy Hunt and David Cameron find a way to avoid a strike.
“There has been a fundamental breakdown in trust between the Health Secretary and junior doctors, which is bad for the NHS and bad for patients.
“I have written to the Prime Minister suggesting that an independent mediator is brought in to break the current stand-off. If he dismisses this suggestion, he will be risking patient safety in both the short and long term.”