The Iranian national team's official Twitter accounted posted a photo of a female football fan in the stands of the Azadi Stadium in Tehran, holding a flag as she watched her team play Spain via a broadcast. Iran lost a closely-fought game 1-0.
Pictures from photo agencies show Iranian football fans -- both men and women -- arriving at the Azadi Stadium dressed in their national team's colors.
Iranian women can be seen blowing horns, while others posed for a selfie to record the moment.
Previously, Iran has banned women from watching men's sporting events and breaking the rules could result in arrest, fines or even imprisonment.
According to the Twitter account of Tara Sepehri Far
-- quoting Iranian news sources -- at one point the screening had been canceled.
"But the doors are now open and screening will happen. Just unnecessary drama, anger and inconvenience for the fans who had bought tickets," tweeted Sepehri Far, who works as a Human Rights Watch (HRW) researcher.
HRW has criticized the ban on women, which also runs counter to the FIFA statues, which prohibit gender discrimination. Article Four says discrimination of any kind is "punishable by suspension or expulsion."
However, it remains to be seen whether Wednesday's event signals a permanent shift in allowing Iranian women to watch men's sporting events.
After the game Sergio Ramos, captain of the winning Spain team, tweeted: "They are the ones who won tonight. Hopefully the first of many."
In a statement sent to CNN when Iran played their first World Cup game against Morocco on Saturday, FIFA said President Gianni Infantino had been reassured by Iranian President Hassan Rouhani during a March visit that the ban on women would eventually be lifted, though no time frame was provided.
The Center for Human Rights in Iran also posted photos of women inside the Azadi Stadium, saying: "All they are asking for is to be treated as EQUALS." The Center is not in Iran, but was posting other people's photos.
Spain took a big step towards reaching the knockout stages with their hard-fought win over Iran on Wednesday.
After a stale first 45 minutes, which Spain dominated but rarely threatened, Diego Costa broke the deadlock less than 10 minutes into the second half, albeit with a huge slice of good fortune.
Iran thought they had found the equalizer soon after, but another feather in the cap for the Video Assistant Referee saw the goal correctly ruled out for offside.
Spain's struggles against Iran continued the trend of the big nations struggling in Russia.
Brazil, Argentina and Germany all failed to win their opening games, while France, England and Portugal -- in their second game -- all labored to secure three points against lower-ranked opposition.
Of the top eight favorites to win the World Cup, only Belgium recorded a convincing result, comfortably beating Panama 3-0.
As the first half wore on, Spain were just beginning to show signs of frustration; Isco first contriving to get in David Silva's way in the box, before Jordi Alba slammed his fist into his palm after Sergio Busquets' over hit pass.
The opening half an hour felt more like a training exercise -- 11 attackers against 11 defenders -- and Spain, for the first time, were starting to find holes in the resolute Iranian defense.
Isco was at the heart of it, exchanging neat passes with Andres Iniesta, twisting and turning away from his markers and eventually forcing a corner.
Both Spain's central defenders came up for it, with Gerard Pique getting his head onto the cross and Sergio Ramos flicking the ball across goal for David Silva, but the Manchester City midfielder's acrobatic effort flashed over the crossbar.
Spain's passing was as accurate and relentless as ever but seemed lethargic and lacking in purpose.
Clearly frustrated by what they perceived as Iranian timewasting, they began the second half at a much higher tempo.
Isco wasted two good chances in front of goal after some brilliant team buildup, but it now felt like a matter of when, not if, Spain would break the deadlock.
Minutes later, the opening finally came. Costa, scorer of two goals in the opening game against Portugal, spun on the ball in the box, before a huge slice of good fortune saw the ball ricochet off Hosseini's leg, back onto Costa and into the back of the net.
But it wouldn't be long before Iran shocked the former world champions and drew level -- or so they thought.
After a huge goalmouth scramble, Saeid Ezatolahi drove the ball through David de Gea's legs and wheeled away in celebration, soon being joined by his teammates and the entire bench.
It wasn't long, however, before referee Andres Cunha, his hand to his earpiece, had the goal analyzed by VAR and subsequently disallowed it.
A tough decision for Iran, but the correct one.
Despite the defeat, Iran still have plenty to play for. They sit just a point behind the top two and victory against Portugal in their final group game would guarantee them a place in the last 16.
Meanwhile FIFA hss fined the Mexican Football Association 10,000 Swiss francs ($10,000) for homophobic chants heard during their World Cup fixture against Germany.
It comes two years after FIFA fined Mexico $30,000
for homophobic chants by supporters on five occasions since November 2015