Voters in Oxfordshire have bucked the national trend by declaring they want to remain in the EU.
The Remain campaign was boosted in Oxford after a 40% majority vote at 02:20 BST.
With a 70% turn out, 70% of people voted to stay in the EU.
In West Oxfordshire, Vale of White Horse and South Oxfordshire, the Remain campaign won by a majority of 7%, 13% and 10% respectively. However, Cherwell voted to leave.
But while David Cameron's constituency of Witney voted to remain, he has announced he will step down as prime minister by October after the UK voted overall to leave the European Union.
On the ground in Witney
Bethan Phillips, BBC political correspondent
The news David Cameron is stepping down has sent a shockwave through his Witney constituency.
He has a lot of loyal supporters here.
He isn't a distant figure in Westminster - he is someone that campaigns here, gets involved in local issues, and during election time, goes door-to-door to gain support.
I was with one local Conservative activist as the news broke - he was visibly shaking with shock. The big question now for Witney - will David Cameron stay on as MP, after he steps down as prime minister?
Labour MP for Oxford East Andrew Smith said there had been a "huge" victory for Remain in the city.
"I think it reflects the nature of our city with the fact we are open, cosmopolitan, we've got a lot of links with Europe and the fact that the university research institutes benefit from EU investment, as indeed does the wider community through our links with BMW," he added.
John Cotton, Conservative leader of South Oxfordshire District Council, who campaigned to leave the EU, has admitted to going "from elation to despair in the space of an hour" following David Cameron's decision to step down as prime minister.
"I can understand completely from his perspective why he would want to go," he said.
"It's a very honourable thing to do, but from the country's point of view we needed him at the helm."
Conservative MP for Didcot and Wantage Ed Vaizey also said he was "sad" to see Mr Cameron go.
He added: "Utterly decent to the end. Loves his country and will continue to work for our future."
Tempers frayed at the Oxford count after city councillor Mike Rowley was ejected from the town hall when he clashed with security staff who refused him entry.
He attempted to enter the venue at about 00:30 BST. After he was halted by door staff, police attended the town hall and restrained the Labour councillor before he was taken home.