Wales will appear in their first semi-final of a major tournament when they play Portugal in Lyon at 20:00 BST.
The winners of that game will face either France or Germany in Sunday's Euro 2016 final.
Fan zones have been set up around Wales, including at Cardiff's Principality Stadium which will hold 27,500 fans who obtained tickets.
An extra 7,500 tickets made available for the Cardiff venue sold out on Wednesday morning in just over an hour.
Those who have secured tickets have been advised to arrive early as extra security measures are in place which may delay entry to the stadium.
Westgate Street in Cardiff will close from 18:00 until 23:30 and Arriva Trains Wales is adding capacity to services where possible.
But Mark Jones, the Blackwood student who campaigned for a Cardiff fan zone, did not manage to get a ticket.
"It's not just gutted for myself but I'm gutted for what seem to be the vast majority of fans who haven't been able to get a ticket and had been to the previous games," he said.
"I can't understand why the council can't open Coopers Field [where the fan zone previously was] as well."
There will also be fan zones in Singleton Park, Swansea, Colwyn Bay, Rhyl, Denbighshire, Aberystwyth, Anglesey, Newport, Pontypridd and Wrexham.
One of the many proud Welshmen watching tonight will be Michael Davies - the head teacher at Joe Allen's former school, Ysgol Y Preseli in Crymych, Pembrokeshire.
He said: "His performances have been quite inspirational - he's the man that brings everything together in terms of the Welsh midfield."
Insurance giant Admiral is closing its Cardiff, Swansea and Newport offices at 19:00 instead of the usual 22:00 so the 600 employees in those sites can watch the game, with staff outside Wales covering customer calls.
Prince Charles has sent a message to the team, saying: "Throughout the whole championship, you have set an inspiring example of teamwork and sportsmanship and I have no doubt that in this latest game you will continue to give your country even greater cause for pride."
First Minister Carwyn Jones said, after waiting 58 years for a place in a major football tournament, "Euro 2016 really is turning into a dream come true for Wales".
Welsh Secretary Alun Cairns added: "You have to look to the fairytale triumph of Leicester City Football Club for something similarly inspiring. This Welsh team truly are the history boys."
At Prime Minister's Questions on Wednesday, David Cameron said: "They have played superbly and we wish them all the best."
The Football Supporters' Federation Cymru said it expected more than 20,000 Welsh fans to head to Lyon.
John Welch, 57, who has made the trip from Australia, said he was "getting goosies" thinking about the game.
Mr Welch, originally of Cardiff but now of Perth, flew from Australia to Lyon after his wife, Jacqui, surprised him with a flight ticket.
The father of five said he was desperate to "be here and taste the atmosphere" - even if it was just in the city's fan zone.
"I didn't think it was possible and then the wife said, 'I've booked this. It's one chance in a lifetime. You might never ever go again.'"
The flight cost Â£1,400 (2,500 Australian dollars).
Martyn O'Rourke, 61, of Ogmore-by-Sea, said it was "fantastic" to be in Lyon.
He said: "I think we'll win. Belgium [who Wales beat 3-1 in the last round] are stronger than Portugal."
His wife, Karen, 59, said it was "definitely" time for Bale to outshine his Real Madrid teammate Cristiano Ronaldo.
The face value of tickets in the semis range from Â£55 (65 euros) to Â£420 (495 euros).
Vince Alm, of the Football Supporters' Federation Cymru, said the pricing was not fair on "real fans".
The prices for those who bought a Follow My Team voucher before the tournament were, however, much cheaper.
Lower category tickets were being sold via ticket agencies, touts and private individuals at about double the face value, he said.
Mr Alm said he expected 12,000 Wales fans to pack into the 59,183-capacity stadium and outnumber those from Portugal.
The fan zone in Lyon's Place Bellecour has a capacity of 20,000, with a big screen and pre-match entertainment.
Thousands of Wales fans have travelled to France for the biggest football match in the nation's history.