Sterling jumped from below $1.47 to above $1.48, after polls from YouGov and ComRes suggested that Brits will vote to remain in the European Union.
Just over a week ago, the pound was trading at around $1.41, as investors feared a victory for the Leave campaign.
However, a string of new polls have seen the currency soar, while European stock markets have also turned green.
The night before polling day, a poll from ComRes revealed an eight-point lead for campaigners who want the UK to stay in the EU, with Remain on 54 per cent and Leave on 46 per cent.
Meanwhile, an online poll conducted by YouGov between 20 June and 22 June showed Remain on 51 per cent, and Leave on 49 per cent. The result reverses the previously-published YouGov poll that had used research from two days earlier, at which point Leave was on 51 per cent, and Remain was on 49 per cent.
"Two massive poll boosts for Remain with voting starting in less than nine hours," said polling expert Mike Smithson.
Despite the polling boost for Remain, the outcome of the referendum remains highly uncertain. All current phone polls have Remain in the lead, while most of the online polls favour Leave, according to Smithson.
Earlier in the day, an online poll from Opinium showed Remain to be backed by 44 per cent of respondents, while Leave received 45 per cent support.
Another poll, from market research company TNS, also showed a narrow lead for the Leave camp.
Luke Taylor from TNS said: "With a race as close as this, the turnout level among different demographic groups will be critical in determining the result."