The game kicks off at 1000 GMT in front of an anticipated sell-out crowd of about 75,000 at Stadium Australia.
It will be the final act of a tournament full of shocks which began one month ago and started with 32 teams, making it the biggest Women's World Cup ever.
Now they are down to the last two and it's a final too close to call. Neither team has ever got this far before.
The two sides last met at the European Championship last summer, when hosts England squeezed into the semi-finals 2-1 in extra time and went on to lift the trophy.
Coach Sarina Wiegman and defender Millie Bright said they were attempting to think of this as just another game, but the skipper admitted there was no getting away from the enormity of the occasion.
British media has been full of references to 1966 -- when the country won the men's World Cup for the only time.
"We know how passionate our nation is back home and how much they want us to win," Bright said on Saturday.
"But for us there is a process, we have a game plan to execute and we need to play the game of our lives."
Chelsea attacker Lauren James is back from a two-match ban for stamping on an opponent in the last-16 victory on penalties over Nigeria.
It would be a surprise, however, if Wiegman makes any changes to the side that impressively saw off Colombia 2-1 and then disposed of co-hosts Australia in the semi-final.
'Next question'
England have been mostly ruthless and machine-like in reaching the final, especially in silencing the home crowd in the 3-1 victory over Australia.
Spain are more slick and have often passed their opponents into submission, coupled with sparks of attacking flair.
England are unbeaten at the tournament, but a notable blip for Jorge Vilda's side was their 4-0 drubbing to a Japan team which hit Spain at pace on the counterattack in the group phase.
Spain had never even won a knockout match at the World Cup until this edition and their exploits are even more impressive for the turmoil that threatened to torpedo their chances.
In September last year, 15 players -- many of them from European powerhouse Barcelona -- came out and said they no longer wanted to represent their country.
They had numerous complaints, but their chief issue was with Vilda -- how strict he was, his lack of success, his tactics and his methods.
Three of the 15 mutineers returned for the World Cup and one of them, Barcelona midfield schemer Aitana Bonmati, has been among the best players at the tournament.
Vilda has been asked repeatedly by reporters at the World Cup about the missing players and was once quizzed if the ones he brought to Australia and New Zealand even liked him.
On the eve of the final he appeared to have had enough of that line of questioning, replying: "Next question, please."
He was more forthright about the spirit among his players, saying they were "united".
"The training sessions, the games, everything that's happened outside has been extraordinary," he said.
"They will have memories for the rest of their lives."
